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Huang J, Ding W, Zhu X, Li B, Zeng F, Wu K, Wu X, Wang F. Ligand Evolution in the Photoactivatable Platinum(IV) Anticancer Prodrugs. Front Chem 2022; 10:876410. [PMID: 35755267 PMCID: PMC9218644 DOI: 10.3389/fchem.2022.876410] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 04/22/2022] [Indexed: 11/24/2022] Open
Abstract
Photoactivatable Pt(IV) anticancer prodrugs with the structure of [PtIV(N1)(N2)(L1)(L2)(A1)(A2)], where N1 and N2 are non-leaving nitrogen donor ligands, L1 and L2 are leaving ligands, and A1 and A2 are axial ligands, have attracted increasing attention due to their promising photo-cytotoxicity even to cisplatin-resistant cancer cells. These photochemotherapeutic prodrugs have high dark-stability under physiological conditions, while they can be activated by visible light restrained at the disease areas, as a consequence showing higher spatial and temporal controllability and much more safety than conventional chemotherapy. The coordinated ligands to the Pt center have been proved to be pivotal in determining the function and activity of the photoactivatable Pt(IV) prodrugs. In this review, we will focus on the development of the coordinated ligands in such Pt(IV) prodrugs and discuss the effects of diverse ligands on their photochemistry and photoactivity as well as the future evolution directions of the ligands. We hope this review can help to facilitate the design and development of novel photoactivatable Pt(IV) anticancer prodrugs.
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Affiliation(s)
- Jingjing Huang
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, China
| | - Weize Ding
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, China
| | - Xingfan Zhu
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, China
| | - Bingbing Li
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, China
| | - Fangang Zeng
- School of Environment and Natural Resources, Renmin University of China, Beijing, China
| | - Kui Wu
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, China
| | - Xiaoqin Wu
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, China
| | - Fuyi Wang
- College of Traditional Chinese Medicine, Shandong University of Traditional Chinese Medicine, Jinan, China.,Beijing National Laboratory for Molecular Sciences, National Centre for Mass Spectrometry in Beijing, CAS Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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2
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Hou Y, Gan T, Fang T, Zhao Y, Luo Q, Liu X, Qi L, Zhang Y, Jia F, Han J, Li S, Wang S, Wang F. OUP accepted manuscript. Nucleic Acids Res 2022; 50:3070-3082. [PMID: 35258624 PMCID: PMC8989551 DOI: 10.1093/nar/gkac151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 02/16/2022] [Accepted: 02/20/2022] [Indexed: 11/23/2022] Open
Abstract
Pyridostatin (PDS) is a well-known G-quadruplex (G4) inducer and stabilizer, yet its target genes have remained unclear. Herein, applying MS proteomics strategy, we revealed PDS significantly downregulated 22 proteins but upregulated 16 proteins in HeLa cancer cells, of which the genes both contain a number of G4 potential sequences, implying that PDS regulation on gene expression is far more complicated than inducing/stabilizing G4 structures. The PDS-downregulated proteins consequently upregulated 6 proteins to activate cyclin and cell cycle regulation, suggesting that PDS itself is not a potential anticancer agent, at least toward HeLa cancer cells. Importantly, SUB1, which encodes human positive cofactor and DNA lesion sensor PC4, was downregulated by 4.76-fold. Further studies demonstrated that the downregulation of PC4 dramatically promoted the cytotoxicity of trans-[PtCl2(NH3)(thiazole)] (trans-PtTz) toward HeLa cells to a similar level of cisplatin, contributable to retarding the repair of 1,3-trans-PtTz crosslinked DNA lesion mediated by PC4. These findings not only provide new insights into better understanding on the biological functions of PDS but also implicate a strategy for the rational design of novel multi-targeting platinum anticancer drugs via conjugation of PDS as a ligand to the coordination scaffold of transplatin for battling drug resistance to cisplatin.
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Affiliation(s)
- Yinzhu Hou
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
- College of Chemical Science, University of Chinese Academy of Sciences, Yuquan Road, Shijingshan District, 100049 Beijing, P.R. China
| | - Tieliang Gan
- College of Chemical Science, University of Chinese Academy of Sciences, Yuquan Road, Shijingshan District, 100049 Beijing, P.R. China
| | - Tiantian Fang
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
| | - Yao Zhao
- Correspondence may also be addressed to Yao Zhao. Tel: +86 010 62529069;
| | - Qun Luo
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
- College of Chemical Science, University of Chinese Academy of Sciences, Yuquan Road, Shijingshan District, 100049 Beijing, P.R. China
| | - Xingkai Liu
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
- College of Chemical Science, University of Chinese Academy of Sciences, Yuquan Road, Shijingshan District, 100049 Beijing, P.R. China
| | - Luyu Qi
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
- College of Chemical Science, University of Chinese Academy of Sciences, Yuquan Road, Shijingshan District, 100049 Beijing, P.R. China
| | - Yanyan Zhang
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
| | - Feifei Jia
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
| | - Juanjuan Han
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
| | - Shumu Li
- Beijing National Laboratory for Molecular Sciences; CAS Key Laboratory of Analytical Chemistry for Living Biosystems; National Centre for Mass Spectrometry in Beijing, Institute of Chemistry, Chinese Academy of Sciences, No. 2 Zhongguancun North First Street, Haidian District, 100190 Beijing, P.R. China
| | - Shijun Wang
- Correspondence may also be addressed to Shijun Wang. Tel: +86 0531 89628750;
| | - Fuyi Wang
- To whom correspondence should be addressed. Tel: +86 010 62529069;
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3
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Mu M, Gao H. Density functional study of trans,trans,trans-[Pt(N 3) 2(OH) 2(Py) 2] on molecular structure and vibrational spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 261:120022. [PMID: 34116418 DOI: 10.1016/j.saa.2021.120022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 05/11/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
This study records the selection of the best combination of geometric optimization and frequency calculation methods of the trans,trans,trans-[Pt(N3)2(OH)2(py)2](FM-190) by using different density functional calculation methods and basis sets. The results show that the CAM-B3LYP/SDD method has the best fit to the experimental data for geometric optimization, while the LSDA/SDD method has better performance in frequency calculation, and the infrared vibration peak is assigned. In addition, the calculated HOMO and LUMO show the energy gap and the internal charge transfer of this complex. The hyperconjugation of the pyridine ring have been explained by NBO analysis.
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Affiliation(s)
- Meilin Mu
- School of Life Science, Ludong University, Yantai, Shandong 264025, China
| | - Hongwei Gao
- School of Life Science, Ludong University, Yantai, Shandong 264025, China.
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4
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Research progress of azido-containing Pt(IV) antitumor compounds. Eur J Med Chem 2021; 227:113927. [PMID: 34695775 DOI: 10.1016/j.ejmech.2021.113927] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/10/2021] [Accepted: 10/13/2021] [Indexed: 12/11/2022]
Abstract
Cancer is a long-known incurable disease, and the medical use of cisplatin has been a significant discovery. However, the side-effects of cisplatin necessitate the development of new and improved drug. Therefore, in this study, we focused on the photoactivatable Pt(IV) compounds Pt[(X1)(X2)(Y1)(Y2)(N3)2], which have a completely novel mechanism of action. Pt(IV) can efficiently overcome the side-effects of cisplatin and other drugs. Here, we have demonstrated, summarized and discussed the effects and mechanism of these compounds. Compared to the relevant articles in the literature, we have provided a more detailed introduction and a made comprehensive classification of these compounds. We believe that our results can effectively provide a reference for the development of these drugs.
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5
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Freitag L, González L. The Role of Triplet States in the Photodissociation of a Platinum Azide Complex by a Density Matrix Renormalization Group Method. J Phys Chem Lett 2021; 12:4876-4881. [PMID: 34006109 PMCID: PMC8165699 DOI: 10.1021/acs.jpclett.1c00829] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 05/13/2021] [Indexed: 06/12/2023]
Abstract
Platinum azide complexes are appealing anticancer photochemotherapy drug candidates because they release cytotoxic azide radicals upon light irradiation. Here we present a density matrix renormalization group self-consistent field (DMRG-SCF) study of the azide photodissociation mechanism of trans,trans,trans-[Pt(N3)2(OH)2(NH3)2], including spin-orbit coupling. We find a complex interplay of singlet and triplet electronic excited states that falls into three different dissociation channels at well-separated energies. These channels can be accessed either via direct excitation into barrierless dissociative states or via intermediate doorway states from which the system undergoes non-radiative internal conversion and intersystem crossing. The high density of states, particularly of spin-mixed states, is key to aid non-radiative population transfer and enhance photodissociation along the lowest electronic excited states.
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6
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Imberti C, Zhang P, Huang H, Sadler PJ. New Designs for Phototherapeutic Transition Metal Complexes. Angew Chem Int Ed Engl 2020; 59:61-73. [PMID: 31310436 PMCID: PMC6973108 DOI: 10.1002/anie.201905171] [Citation(s) in RCA: 234] [Impact Index Per Article: 58.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/19/2019] [Indexed: 12/17/2022]
Abstract
In this Minireview, we highlight recent advances in the design of transition metal complexes for photodynamic therapy (PDT) and photoactivated chemotherapy (PACT), and discuss the challenges and opportunities for the translation of such agents into clinical use. New designs for light-activated transition metal complexes offer photoactivatable prodrugs with novel targeted mechanisms of action. Light irradiation can provide spatial and temporal control of drug activation, increasing selectivity and reducing side-effects. The photophysical and photochemical properties of transition metal complexes can be controlled by the appropriate choice of the metal, its oxidation state, the number and types of ligands, and the coordination geometry.
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Affiliation(s)
- Cinzia Imberti
- Department of ChemistryUniversity of WarwickCoventryCV4 7ALUK
| | - Pingyu Zhang
- College of Chemistry and Environmental EngineeringShenzhen UniversityShenzhen518060China
- Department of ChemistryUniversity of WarwickCoventryCV4 7ALUK
| | - Huaiyi Huang
- School of Pharmaceutical Science (Shenzhen)Sun Yat-sen UniversityGuangzhou510275China
- Department of ChemistryUniversity of WarwickCoventryCV4 7ALUK
| | - Peter J. Sadler
- Department of ChemistryUniversity of WarwickCoventryCV4 7ALUK
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7
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Chen CKJ, Gui X, Kappen P, Renfrew AK, Hambley TW. The effect of charge on the uptake and resistance to reduction of platinum(IV) complexes in human serum and whole blood models. Metallomics 2020; 12:1599-1615. [PMID: 33084707 DOI: 10.1039/d0mt00157k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
cis- and trans-Platinum(iv) complexes with diaminetetracarboxylate coordination spheres possess the highly desirable property of exhibiting unusual resistance to reduction by blood serum components and endogenous reductants such as ascorbate. At the same time they are rapidly reduced in the intracellular environment of cancer cells. Consequently, they can potentially be tuned to remain intact in vivo until arrival at the tumour target where they are rapidly reduced to yield the active platinum(ii) species. However, in order to achieve this, uptake must be largely restricted to tumour cells and therefore uptake by healthy cells including red blood cells must be prevented. In this proof of concept study, we report on the effect of net charge as a means of controlling the uptake by red blood cells. Using 1H NMR spectroscopy we found that modifying the net charge of the complex does not influence the rate of reduction of the complexes by an excess of ascorbate. Using XANES spectroscopy we found that modifying the net charge of the platinum(iv) complexes decreased the extent of reduction in whole blood, although probably not to the degree needed for the optimal delivery to tumours. Therefore, it is likely to be necessary to adopt higher charges and/or additional strategies to keep platinum(iv) prodrugs out of blood cells.
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Affiliation(s)
| | - Xiao Gui
- School of Chemistry, The University of Sydney, NSW, Australia.
| | - Peter Kappen
- Australian Synchrotron, ANSTO, 800 Blackburn Road, Clayton 3168, Victoria, Australia
| | - Anna K Renfrew
- School of Chemistry, The University of Sydney, NSW, Australia.
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8
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Nikahd S, Babadi Aghakhanpour R, Nabavizadeh SM, Niroomand Hosseini F, Hoseini SJ, Pfitzner A, Samandar Sangari M. Luminescent mononuclear and dinuclear cycloplatinated (II) complexes comprising azide and phosphine ancillary ligands. Appl Organomet Chem 2019. [DOI: 10.1002/aoc.5197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sahebeh Nikahd
- Professor Rashidi Laboratory of Organometallic Chemistry, Department of Chemistry, College of SciencesShiraz University Shiraz 71467‐13565 Iran
| | | | - S. Masoud Nabavizadeh
- Professor Rashidi Laboratory of Organometallic Chemistry, Department of Chemistry, College of SciencesShiraz University Shiraz 71467‐13565 Iran
| | | | - S. Jafar Hoseini
- Professor Rashidi Laboratory of Organometallic Chemistry, Department of Chemistry, College of SciencesShiraz University Shiraz 71467‐13565 Iran
| | - Arno Pfitzner
- Institut für Anorganische ChemieUniversität Regensburg 93040 Regensburg Germany
| | - Mozhgan Samandar Sangari
- Professor Rashidi Laboratory of Organometallic Chemistry, Department of Chemistry, College of SciencesShiraz University Shiraz 71467‐13565 Iran
- Institut für Anorganische ChemieUniversität Regensburg 93040 Regensburg Germany
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9
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Renfrew AK, Karges J, Scopelliti R, Bobbink FD, Nowak‐Sliwinska P, Gasser G, Dyson PJ. Towards Light‐Activated Ruthenium–Arene (RAPTA‐Type) Prodrug Candidates. Chembiochem 2019; 20:2876-2882. [DOI: 10.1002/cbic.201900236] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Indexed: 12/18/2022]
Affiliation(s)
- Anna K. Renfrew
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Johannes Karges
- Chimie ParisTechPSL UniversityCNRSInstitute of Chemistry for Life and Health SciencesLaboratory for Inorganic Chemical Biology 75005 Paris France
| | - Rosario Scopelliti
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Felix D. Bobbink
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Patrycja Nowak‐Sliwinska
- Institute of Pharmaceutical Sciences of Western Switzerland andTranslational Research Center in Oncohaematology 1211 Geneva 4 Switzerland
| | - Gilles Gasser
- Chimie ParisTechPSL UniversityCNRSInstitute of Chemistry for Life and Health SciencesLaboratory for Inorganic Chemical Biology 75005 Paris France
| | - Paul J. Dyson
- Institut des Sciences et Ingénierie ChimiquesEcole Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
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10
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Imberti C, Zhang P, Huang H, Sadler PJ. New Designs for Phototherapeutic Transition Metal Complexes. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905171] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Cinzia Imberti
- Department of Chemistry University of Warwick Coventry CV4 7AL UK
| | - Pingyu Zhang
- College of Chemistry and Environmental Engineering Shenzhen University Shenzhen 518060 China
- Department of Chemistry University of Warwick Coventry CV4 7AL UK
| | - Huaiyi Huang
- School of Pharmaceutical Science (Shenzhen) Sun Yat-sen University Guangzhou 510275 China
- Department of Chemistry University of Warwick Coventry CV4 7AL UK
| | - Peter J. Sadler
- Department of Chemistry University of Warwick Coventry CV4 7AL UK
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11
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Gurruchaga-Pereda J, Martínez Á, Terenzi A, Salassa L. Anticancer platinum agents and light. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2019.118981] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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12
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Yu Y, Xu Q, He S, Xiong H, Zhang Q, Xu W, Ricotta V, Bai L, Zhang Q, Yu Z, Ding J, Xiao H, Zhou D. Recent advances in delivery of photosensitive metal-based drugs. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.01.020] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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13
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Shi H, Imberti C, Sadler PJ. Diazido platinum(iv) complexes for photoactivated anticancer chemotherapy. Inorg Chem Front 2019. [DOI: 10.1039/c9qi00288j] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Diazido Pt(iv) complexes with a general formula [Pt(N3)2(L)(L′)(OR)(OR′)] are a new generation of anticancer prodrugs designed for use in photoactivated chemotherapy.
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Affiliation(s)
- Huayun Shi
- Department of Chemistry
- University of Warwick
- Coventry
- UK
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14
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Shi H, Romero-Canelón I, Hreusova M, Novakova O, Venkatesh V, Habtemariam A, Clarkson GJ, Song JI, Brabec V, Sadler PJ. Photoactivatable Cell-Selective Dinuclear trans-Diazidoplatinum(IV) Anticancer Prodrugs. Inorg Chem 2018; 57:14409-14420. [PMID: 30365308 PMCID: PMC6257630 DOI: 10.1021/acs.inorgchem.8b02599] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
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A series of dinuclear
octahedral PtIV complexes trans,trans,trans-[{Pt(N3)2(py)2(OH)(OC(O)CH2CH2C(O)NH)}2R] containing pyridine (py) and bridging
dicarboxylate [R = −CH2CH2– (1), trans-1,2-C6H10– (2), p-C6H4– (3), −CH2CH2CH2CH2– (4)] ligands have
been synthesized and characterized, including the X-ray crystal structures
of complexes 1·2MeOH and 4, the first
photoactivatable dinuclear PtIV complexes with azido ligands.
The complexes are highly stable in the dark, but upon photoactivation
with blue light (420 nm), they release the bridging ligand and mononuclear
photoproducts. Upon irradiation with blue light (465 nm), they generate
azidyl and hydroxyl radicals, detected using a 5,5-dimethyl-1-pyrroline N-oxide electron paramagnetic resonance spin trap, accompanied
by the disappearance of the ligand-to-metal charge-transfer (N3 → Pt) band at ca. 300 nm. The dinuclear complexes
are photocytotoxic to human cancer cells (465 nm, 4.8 mW/cm2, 1 h), including A2780 human ovarian and esophageal OE19 cells with
IC50 values of 8.8–78.3 μM, whereas cisplatin
is inactive under these conditions. Complexes 1, 3, and 4 are notably more photoactive toward
cisplatin-resistant ovarian A2780cis compared to A2780 cells. Remarkably,
all of the complexes were relatively nontoxic toward normal cells
(MRC5 lung fibroblasts), with IC50 values >100 μM,
even after irradiation. The introduction of an aromatic bridging ligand
(3) significantly enhanced cellular uptake. The populations
in the stages of the cell cycle remained unchanged upon treatment
with complexes in the dark, while the population of the G2/M phase
increased upon irradiation, suggesting that DNA is a target for these
photoactivated dinuclear PtIV complexes. Liquid chromatography–mass
spectrometry data show that the photodecomposition pathway of the
dinuclear complexes results in the release of two molecules of mononuclear
platinum(II) species. As a consequence, DNA binding of the dinuclear
complexes after photoactivation in cell-free media is, in several
respects, qualitatively similar to that of the photoactivated mononuclear
complex FM-190. After photoactivation, they were 2-fold
more effective in quenching the fluorescence of EtBr bound to DNA,
forming DNA interstrand cross-links and unwinding DNA compared to
the photoactivated FM-190. Novel all-trans dinuclear
PtIV complexes bridged
by a dicarboxylate linker, highly stable in the dark, generate azidyl
and hydroxyl radicals upon irradiation with blue light. They are photocytotoxic
to human cancer cells, whereas cisplatin was inactive under these
conditions and more photoactive toward cisplatin-resistant ovarian
cancer cells compared to wild-type cells. Remarkably, the dinuclear
complexes were relatively nontoxic toward normal human cells. Cell
cycle and DNA binding experiments suggested that DNA is a target.
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Affiliation(s)
- Huayun Shi
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K
| | - Isolda Romero-Canelón
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K.,School of Pharmacy, Institute of Clinical Sciences , University of Birmingham , Birmingham B15 2TT , U.K
| | - Monika Hreusova
- Department of Biophysics, Faculty of Science , Palacky University , 17 listopadu 12 , Olomouc CZ-77146 , Czech Republic.,Institute of Biophysics , Czech Academy of Sciences , Kralovopolska 135 , Brno CZ-61265 , Czech Republic
| | - Olga Novakova
- Institute of Biophysics , Czech Academy of Sciences , Kralovopolska 135 , Brno CZ-61265 , Czech Republic
| | - V Venkatesh
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K
| | - Abraha Habtemariam
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K
| | - Guy J Clarkson
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K
| | - Ji-Inn Song
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K
| | - Viktor Brabec
- Institute of Biophysics , Czech Academy of Sciences , Kralovopolska 135 , Brno CZ-61265 , Czech Republic
| | - Peter J Sadler
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , U.K
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15
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Abstract
The success of platinum-based anticancer agents has motivated the exploration of novel metal-based drugs for several decades, whereas problems such as drug-resistance and systemic toxicity hampered their clinical applications and efficacy. Stimuli-responsiveness of some metal complexes offers a good opportunity for designing site-specific prodrugs to maximize the therapeutic efficacy and minimize the side effect of metallodrugs. This review presents a comprehensive and up-to-date overview on the therapeutic stimuli-responsive metallodrugs that have appeared in the past two decades, where stimuli such as redox, pH, enzyme, light, temperature, and so forth were involved. The compounds are classified into three major categories based on the nature of stimuli, that is, endo-stimuli-responsive metallodrugs, exo-stimuli-responsive metallodrugs, and dual-stimuli-responsive metallodrugs. Representative examples of each type are discussed in terms of structure, response mechanism, and potential medical applications. In the end, future opportunities and challenges in this field are tentatively proposed. With diverse metal complexes being introduced, the foci of this review are pointed to platinum and ruthenium complexes.
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Affiliation(s)
- Xiaohui Wang
- College of Chemistry and Molecular Engineering , Nanjing Tech University , Nanjing 211816 , P. R. China
| | - Xiaoyong Wang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences , Nanjing University , Nanjing 210023 , P. R. China
| | - Suxing Jin
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences , Nanjing University , Nanjing 210023 , P. R. China
| | - Nafees Muhammad
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry , Sun Yat-Sen University , Guangzhou 510275 , P. R. China
| | - Zijian Guo
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210093 , P. R. China
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16
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Potentiation of cytotoxic action of cis -[PtCl 2 (NH 3 )(1M7AI)] by UVA irradiation. Mechanistic insights. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.06.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Mitra K. Platinum complexes as light promoted anticancer agents: a redefined strategy for controlled activation. Dalton Trans 2018; 45:19157-19171. [PMID: 27883129 DOI: 10.1039/c6dt03665a] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Site-specific delivery and amenable activation of prodrugs are indispensible criteria for designing novel anticancer agents. Platinum based drugs vanguard the chemotherapeutic regimes and over the years significant attention has been paid to achieve more efficacious drugs with fewer adverse effects. The switch from platinum(ii) drugs to the inert platinum(iv) analogues proved advantageous but the new prodrugs still suffered from unspecific cytotoxic actions. Thus the photoactivation of an inert platinum prodrug specifically within neoplastic cells provided the desired spatio-temporal control over drug activation by means of illumination, thereby limiting the cytotoxic events to only at the targeted tumors. This article collates research on platinum complexes which exhibit potential light mediated anticancer effects and provides insights into the underlying mechanisms of activation. Fine tuning of the coordination sphere results in dramatic alteration of the redox and spectral properties of both ground and excited states and the cellular properties of the molecules. This concise article highlights the various light promoted strategies employed to attain a controlled release of active platinum(ii) and/or reactive oxygen species such as photoreduction, photocaging, photodissociation and photosensitization. Such dual action photoactive metal complexes with improved aqueous solubility and versatility are promising candidates for combination therapy which is likely to be the future of anticancer research.
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Affiliation(s)
- Koushambi Mitra
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560-012, India.
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Hu X, Li F, Noor N, Ling D. Platinum drugs: from Pt(II) compounds, Pt(IV) prodrugs, to Pt nanocrystals/nanoclusters. Sci Bull (Beijing) 2017; 62:589-596. [PMID: 36659367 DOI: 10.1016/j.scib.2017.03.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/02/2017] [Accepted: 03/03/2017] [Indexed: 01/21/2023]
Abstract
Platinum (Pt) based drugs, such as cisplatin, are widely used as anti-cancer agents, but their severe adverse reactions and resistance of cancer patients have limited their board clinical use. For the last few decades, Pt(II) compounds, Pt(IV) prodrugs as well as smart drug delivery systems have been developed to overcome these problems. However, most conventional strategies rely on the similar anti-cancer mechanism with cisplatin and consequently only achieve limited success. Recently, Pt nanocrystals/nanoclusters (Pt NCs), with a brand new anti-cancer mechanism, have shown a promising potential in targeted cancer therapy, especially in Pt resistance circumvention. This review is helpful to understand the research strategies of Pt drugs, particularly, the recent developments and medical applications of Pt NCs.
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Affiliation(s)
- Xi Hu
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Fangyuan Li
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; Key Laboratory of Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou 310027, China
| | - Nabila Noor
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Daishun Ling
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; Key Laboratory of Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou 310027, China.
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Tsipis AC, Karapetsas IN. Prediction of 195 Pt NMR of photoactivable diazido- and azine-Pt(IV) anticancer agents by DFT computational protocols. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:145-153. [PMID: 27628024 DOI: 10.1002/mrc.4523] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/03/2016] [Accepted: 09/05/2016] [Indexed: 06/06/2023]
Abstract
195 Pt NMR chemical shifts for a series of large-sized photoactivable anticancer diazido-Pt(IV), homopiperizine-Pt(IV) and multifunctional azine-Pt(IV) complexes hardly to be probed experimentally and by sophisticated four-component and two-component relativistic calculations are predicted with high accuracy by density functional theory computational protocols. The calculated 195 Pt NMR chemical shifts constitute a crucial descriptor for making highly predictive one-parameter quantitative structure activity relationships models that help in designing photoactivable Pt(IV)-based antitumor agents with high cytotoxicity and selectivity. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Athanassios C Tsipis
- Laboratory of Inorganic and General Chemistry, Department of Chemistry, University of Ioannina, Ioannina, Greece
| | - Ioannis N Karapetsas
- Laboratory of Inorganic and General Chemistry, Department of Chemistry, University of Ioannina, Ioannina, Greece
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Karmakar S, Chatterjee S, Purkait K, Mukherjee A. Anticancer activity of a chelating nitrogen mustard bearing tetrachloridoplatinum(iv) complex: better stability yet equipotent to the Pt(ii) analogue. Dalton Trans 2016; 45:11710-22. [PMID: 27230464 DOI: 10.1039/c6dt00831c] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Two Pt(iv) complexes cis,cis,trans-[Pt(IV)(L1)Cl4] (1a) & cis,cis,trans-[Pt(IV)(L2)Cl4] (2a) containing the nitrogen mustard moieties -N(CH2CH2Cl)2 & -NHCH2CH2Cl, were prepared in a single step from the Pt(ii) complexes containing -N(CH2CH2OH)2 (1) & -NHCH2CH2OH (2) moieties respectively using only thionyl chloride. The characterization of both the Pt(iv) complexes was performed by NMR, IR, UV and elemental analysis. Complex 1a was also characterized by single crystal X-ray diffraction. 1a crystallized in the I2/a space group. 1a exhibited much higher solution stability than 2a in kinetic studies by (1)H NMR. 1a shows a prodrug like activity as it converts to its Pt(ii) congener, [Pt(II)(L1)Cl2] (3) after 2 days in buffered solution. The binding experiment of 1a with model nucleobase 9-ethylguanine (9-EtG), showed that 1a converts to 3 and forms mono-adducts with 9-EtG. In the presence of reduced glutathione (GSH), the formation of 3 from 1a is quicker and upon the formation of 3 it binds almost instantaneously to GSH to form cis-[PtCl(L1)SG] (3c). Complex 3c transformed within a day to give a free aziridinium ion of L1 (3b) by dissociation. The in vitro cytotoxicity of the complexes and the clinical anticancer drug cisplatin show that 1a is potent against MCF-7, A549, HepG2 and MIA PaCa-2. The potency is highest against MIA PaCa-2 exhibiting an IC50 value of 4.4 ± 0.5 μM. The in vitro cytotoxicity data also showed that between the two complexes only 1a is active against MCF-7, A549 and MIA PaCa-2 in normoxia and hypoxia, both in the presence and absence of added GSH. Even in the presence of excess GSH in hypoxia, 1a exhibits significant cytotoxicity against MIA PaCa-2 and MCF-7 with IC50 values of 4.5 ± 0.3 and 11.2 ± 1.8 μM respectively. Platinum accumulation studies by ICP-MS display greater internalization of 1a, than 2a, 3 and cisplatin inside MCF-7 cells. 1a arrests cell cycle at the G2/M phase in MCF-7, exhibits capability to inhibit metastasis, induces apoptotic cell death and displays blood compatibility with human blood.
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Affiliation(s)
- Subhendu Karmakar
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur-741246, India.
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21
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Fanelli M, Formica M, Fusi V, Giorgi L, Micheloni M, Paoli P. New trends in platinum and palladium complexes as antineoplastic agents. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2015.11.004] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Shaili E, Fernández-Giménez M, Rodríguez-Astor S, Gandioso A, Sandín L, García-Vélez C, Massaguer A, Clarkson GJ, Woods JA, Sadler PJ, Marchán V. A Photoactivatable Platinum(IV) Anticancer Complex Conjugated to the RNA Ligand Guanidinoneomycin. Chemistry 2015; 21:18474-86. [PMID: 26662220 DOI: 10.1002/chem.201502373] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Indexed: 11/07/2022]
Abstract
A photoactivatable platinum(IV) complex, trans,trans,trans-[Pt(N3 )2 (OH)(succ)(py)2 ] (succ=succinylate, py=pyridine), has been conjugated to guanidinoneomycin to study the effect of this guanidinum-rich compound on the photoactivation, intracellular accumulation and phototoxicity of the pro-drug. Surprisingly, trifluoroacetic acid treatment causes the replacement of an azido ligand and the axial hydroxide ligand by trifluoroacetate, as shown by NMR spectroscopy, MS and X-ray crystallography. Photoactivation of the platinum-guanidinoneomycin conjugate in the presence of 5'-guanosine monophosphate (5'-GMP) led to the formation of trans-[Pt(N3 )(py)2 (5'-GMP)](+) , as does the parent platinum(IV) complex. Binding of the platinum(II) photoproduct {PtN3 (py)2 }(+) to guanine nucleobases in a short single-stranded oligonucleotide was also observed. Finally, cellular uptake studies showed that guanidinoneomycin conjugation improved the intracellular accumulation of the platinum(IV) pro-drug in two cancer cell lines, particularly in SK-MEL-28 cells. Notably, the higher phototoxicity of the conjugate in SK-MEL-28 cells than in DU-145 cells suggests a degree of selectivity towards the malignant melanoma cell line.
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Affiliation(s)
- Evyenia Shaili
- Department of Chemistry, University of Warwick, Warwick, CV4 7AL, Coventry (UK)
| | - Marta Fernández-Giménez
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona (Spain)
| | - Savina Rodríguez-Astor
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona (Spain)
| | - Albert Gandioso
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona (Spain)
| | - Lluís Sandín
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona (Spain)
| | - Carlos García-Vélez
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona (Spain)
| | - Anna Massaguer
- Departament de Biologia, Universitat de Girona, Campus Montilivi, 17071, Girona (Spain)
| | - Guy J Clarkson
- Department of Chemistry, University of Warwick, Warwick, CV4 7AL, Coventry (UK)
| | - Julie A Woods
- Photobiology Unit, Department of Dermatology, Ninewells Hospital, Dundee, DD1 9SY (UK)
| | - Peter J Sadler
- Department of Chemistry, University of Warwick, Warwick, CV4 7AL, Coventry (UK).
| | - Vicente Marchán
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona (Spain).
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Pizarro AM, McQuitty RJ, Mackay FS, Zhao Y, Woods JA, Sadler PJ. Cellular Accumulation, Lipophilicity and Photocytotoxicity of Diazido Platinum(IV) Anticancer Complexes. ChemMedChem 2014; 9:1169-75. [DOI: 10.1002/cmdc.201402066] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Indexed: 11/10/2022]
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The Photochemistry of Transition Metal Complexes and Its Application in Biology and Medicine. LUMINESCENT AND PHOTOACTIVE TRANSITION METAL COMPLEXES AS BIOMOLECULAR PROBES AND CELLULAR REAGENTS 2014. [DOI: 10.1007/430_2014_165] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Abstract
Metals have been considered for millennia to have medicinal values. With the advent of modern medicine, many metal-based drugs have proven to be highly effective in the clinic. Many different metal ions have shown activity against a range of diseases. The unique electronic structure of transition metals offers great versatility, not always seen in organic drugs, in terms of the ability to tune the properties of a given molecule. This review gives a brief overview of the most established therapeutic metals, and their more common applications, such as platinum-based anticancer drugs. New developments within the field of metallodrugs and novel strategies being employed to improve methods of delivery, are also discussed.
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26
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Wilson JJ, Lippard SJ. Synthetic methods for the preparation of platinum anticancer complexes. Chem Rev 2013; 114:4470-95. [PMID: 24283498 DOI: 10.1021/cr4004314] [Citation(s) in RCA: 494] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Justin J Wilson
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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Bednarski PJ, Korpis K, Westendorf AF, Perfahl S, Grünert R. Effects of light-activated diazido-PtIV complexes on cancer cells in vitro. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120118. [PMID: 23776289 DOI: 10.1098/rsta.2012.0118] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Various Pt(IV) diazides have been investigated over the years as light-activatable prodrugs that interfere with cell proliferation, accumulate in cancer cells and cause cell death. The potencies of the complexes vary depending on the substituted amines (pyridine=piperidine>ammine) as well as the coordination geometry (trans diazide>cis). Light-activated Pt(IV) diazides tend to be less specific than cisplatin at inhibiting cancer cell growth, but cells resistant to cisplatin show little cross-resistance to Pt(IV) diazides. Platinum is accumulated in the cancer cells to a similar level as cisplatin, but only when activated by light, indicating that reactive Pt species form photolytically. Studies show that Pt also becomes attached to cellular DNA upon the light activation of various Pt(IV) diazides. Structures of some of the photolysis products were elucidated by LC-MS/MS; monoaqua- and diaqua-Pt(II) complexes form that are reactive towards biomolecules such as calf thymus DNA. Platination of calf thymus DNA can be blocked by the addition of nucleophiles such as glutathione and chloride, further evidence that aqua-Pt(II) species form upon irradiation. Evidence is presented that reactive oxygen species may be generated in the first hours following photoactivation. Cell death does not take the usual apoptotic pathways seen with cisplatin, but appears to involve autophagy. Thus, photoactivated diazido-Pt(IV) complexes represent an interesting class of potential anti-cancer agents that can be selectively activated by light and kill cells by a mechanism different to the anti-cancer drug cisplatin.
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Affiliation(s)
- Patrick J Bednarski
- Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, 17487 Greifswald, Germany.
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28
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Zhao Y, Woods JA, Farrer NJ, Robinson KS, Pracharova J, Kasparkova J, Novakova O, Li H, Salassa L, Pizarro AM, Clarkson GJ, Song L, Brabec V, Sadler PJ. Diazido mixed-amine platinum(IV) anticancer complexes activatable by visible-light form novel DNA adducts. Chemistry 2013; 19:9578-91. [PMID: 23733242 PMCID: PMC4280898 DOI: 10.1002/chem.201300374] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Indexed: 01/09/2023]
Abstract
Platinum diam(m)ine complexes, such as cisplatin, are successful anticancer drugs, but suffer from problems of resistance and side-effects. Photoactivatable Pt(IV) prodrugs offer the potential of targeted drug release and new mechanisms of action. We report the synthesis, X-ray crystallographic and spectroscopic properties of photoactivatable diazido complexes trans,trans,trans-[Pt(N3)2(OH)2(MA)(Py)] (1; MA=methylamine, Py=pyridine) and trans,trans,trans-[Pt(N3)2(OH)2(MA)(Tz)] (2; Tz=thiazole), and interpret their photophysical properties by TD-DFT modelling. The orientation of the azido groups is highly dependent on H bonding and crystal packing, as shown by polymorphs 1p and 1q. Complexes 1 and 2 are stable in the dark towards hydrolysis and glutathione reduction, but undergo rapid photoreduction with UVA or blue light with minimal amine photodissociation. They are over an order of magnitude more potent towards HaCaT keratinocytes, A2780 ovarian, and OE19 oesophageal carcinoma cells than cisplatin and show particular potency towards cisplatin-resistant human ovarian cancer cells (A2780cis). Analysis of binding to calf-thymus (CT), plasmids, oligonucleotide DNA and individual nucleotides reveals that photoactivated 1 and 2 form both mono- and bifunctional DNA lesions, with preference for G and C, similar to transplatin, but with significantly larger unwinding angles and a higher percentage of interstrand cross-links, with evidence for DNA strand cross-linking further supported by a comet assay. DNA lesions of 1 and 2 on a 50 bp duplex were not recognised by HMGB1 protein, in contrast to cisplatin-type lesions. The photo-induced platination reactions of DNA by 1 and 2 show similarities with the products of the dark reactions of the Pt(II) compounds trans-[PtCl2(MA)(Py)] (5) and trans-[PtCl2(MA)(Tz)] (6). Following photoactivation, complex 2 reacted most rapidly with CT DNA, followed by 1, whereas the dark reactions of 5 and 6 with DNA were comparatively slow. Complexes 1 and 2 can therefore give rapid potent photocytotoxicity and novel DNA lesions in cancer cells, with no activity in the absence of irradiation.
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Affiliation(s)
- Yao Zhao
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Julie A Woods
- Photobiology Unit, Department of Dermatology, University of DundeeNinewells Hospital and Medical School, Dundee, DD1 9SY (UK)
| | - Nicola J Farrer
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Kim S Robinson
- Photobiology Unit, Department of Dermatology, University of DundeeNinewells Hospital and Medical School, Dundee, DD1 9SY (UK)
| | - Jitka Pracharova
- Faculty of Science, Palacky University, 17Listopadu 12, 77146 Olomouc (Czech Republic)
| | - Jana Kasparkova
- Faculty of Science, Palacky University, 17Listopadu 12, 77146 Olomouc (Czech Republic)
| | - Olga Novakova
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i.Kralovopolska 135, 61265 Brno (Czech Republic)
| | - Huilin Li
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Luca Salassa
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Ana M Pizarro
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Guy J Clarkson
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Lijiang Song
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
| | - Viktor Brabec
- Faculty of Science, Palacky University, 17Listopadu 12, 77146 Olomouc (Czech Republic)
| | - Peter J Sadler
- Department of Chemistry, University of WarwickCoventry, CV4 7AL (UK)
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Fehlhammer WP, Beck W. Azide Chemistry - An Inorganic Perspective, Part I Metal Azides: Overview, General Trends and Recent Developments. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300162] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Lindahl SE, Park H, Pink M, Zaleski JM. Utilizing redox-mediated Bergman cyclization toward the development of dual-action metalloenediyne therapeutics. J Am Chem Soc 2013; 135:3826-33. [PMID: 23432635 DOI: 10.1021/ja308190q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of 2 equiv of 1,2-bis((diphenylphosphino)ethynyl)benzene (dppeb, 1) with Pt(cod)Cl2 followed by treatment with N2H4 yields the reduced Pt(0) metalloenediyne, Pt(dppeb)2, 2. This complex is stable to both air oxidation and metal-mediated Bergman cyclization under ambient conditions due to the nearly idealized tetrahedral geometry. Reaction of 2 with 1 equiv of I2 in the presence of excess 1,4-cyclohexadiene (1,4-CHD) radical trap rapidly and near-quantitatively generates the cis-Bergman-cyclized, diiodo product 3 ((31)P: δ = 41 ppm, J(Pt-P) = 3346 Hz) with concomitant loss of 1 equiv of uncyclized phosphine chelate ((31)P: δ = -33 ppm). In contrast, addition of 2 equiv of I2 in the absence of additional radical trap instantaneously forms a metastable Pt(dppeb)2(2+) intermediate species, 4, that is characterized by δ = 51 ppm in the (31)P NMR (J(Pt-P) = 3171 Hz) and ν(C≡C) = 2169 cm(-1) in the Raman profile, indicating that it is an uncyclized, bis-ligated complex. Over 24 h, 4 undergoes ligand exchange to form a neutral, square planar complex that spontaneously Bergman cyclizes at ambient temperature to give the crystalline product Pt(dppnap-I2)I2 (dppnap-I2 = (1,4-diiodonaphthalene-2,3-diyl)bis(diphenylphosphine)), 5, in 52% isolated yield. Computational analysis of the oxidation reaction proposes two plausible flattened tetrahedral structures for intermediate 4: one where the phosphine core has migrated to a trans-spanning chelate geometry, and a second, higher energy structure (3.3 kcal/mol) with two cis-chelating phosphine ligands (41° dihedral angle) via a restricted alkyne-terminal starting point. While the energies are disparate, the common theme in both structures is the elongated Pt-P bond lengths (>2.4 Å), indicating that nucleophilic ligand substitution by I(-) is on the reaction trajectory to the cyclized product 5. The efficiency of the redox-mediated Bergman cyclization reaction of this stable Pt(0) metalloenediyne prodrug and resulting cisplatin-like byproduct represents an intriguing new strategy for potential dual-threat metalloenediyne therapeutics.
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Affiliation(s)
- Sarah E Lindahl
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
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31
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Butler JS, Woods JA, Farrer NJ, Newton ME, Sadler PJ. Tryptophan Switch for a Photoactivated Platinum Anticancer Complex. J Am Chem Soc 2012; 134:16508-11. [DOI: 10.1021/ja3074159] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Julie A. Woods
- Photobiology Unit, Department
of Dermatology, Ninewells Hospital, Dundee
DD1 9SY, U.K
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Tai HC, Zhao Y, Farrer NJ, Anastasi AE, Clarkson G, Sadler PJ, Deeth RJ. A computational approach to tuning the photochemistry of platinum(IV) anticancer agents. Chemistry 2012; 18:10630-42. [PMID: 22807241 DOI: 10.1002/chem.201200782] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Indexed: 11/11/2022]
Abstract
Diazido Pt(IV) complexes are inert stable prodrugs that can be photoactivated to produce Pt(II) species with promising anticancer activity. Our studies of the photochemistry of Pt(IV) complexes, [Pt(X)(2) (Y)(2) (Z)(2) ](0/-1) (X=N-ligands (NH(3) , pyridine, etc.)/S(CH(3) )(2) /H(-) , Y=(pseudo)halogen (N(3) (-) , I(-) ), Z=OR(-) , R=H, Ac) by time-dependent density functional theory (TDDFT) show close agreement with spectroscopic data. Broad exploration of cis/trans geometries, trans influences, the nature of the OR(-) and (pseudo)halogen ligands, electron-withdrawing/donating/delocalising substituents on the N-ligands, and intramolecular H bonds shows that: 1) the design of platinum(IV) complexes with intense bands shifted towards longer wavelengths (from 289 to ∼330 nm) can be achieved by introducing intramolecular H bonds involving the OH ligands and 2-hydroxyquinoline or by iodido ligands; 2) mesomeric electron-withdrawing substituents on pyridine result in low-energy absorption with significant intensity in the visible region; and 3) the distinct makeup of the molecular orbitals involved in the electronic transitions for cis/trans-{Pt(N(3) )(2) } isomers results in different photoproducts. In general, the comparison of the optimised geometries shows that Pt(IV) complexes with longer PtL bonds are more likely to undergo photoreduction with longer-wavelength light. The novel complex trans,trans,trans-[Pt(N(3) )(2) (OH)(2) (NH(3) )(4-nitropyridine)] with predicted absorption in the visible region has been synthesised. The experimental UV/Vis spectrum in aqueous solution correlates well with the intense band in the computed spectrum, whereas the overlay in the low-energy region can be improved by a solvent model. This combined computational and experimental study shows that TDDFT can be used to tune the coordination environment for optimising photoactive Pt(IV) compounds as anticancer agents.
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Affiliation(s)
- Hui-Chung Tai
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, UK
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Samouei H, Rashidi M, Heinemann FW. A cyclometalated diplatinum complex containing 1,1′-bis(diphenylphosphino)ferrocene as spacer ligand: Antitumor study. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.08.038] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Esmaeilbeig A, Samouei H, Abedanzadeh S, Amirghofran Z. Synthesis, characterization and antitumor activity study of some cyclometalated organoplatinum(II) complexes containing aromatic N-donor ligands. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.06.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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Frezza M, Dou QP, Xiao Y, Samouei H, Rashidi M, Samari F, Hemmateenejad B. In vitro and in vivo antitumor activities and DNA binding mode of five coordinated cyclometalated organoplatinum(II) complexes containing biphosphine ligands. J Med Chem 2011; 54:6166-76. [PMID: 21815643 DOI: 10.1021/jm2006832] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
New complexes [Pt(C(∧)N)Cl(dppa)] (1), and [Pt(C(∧)N)Cl(dppm)] (2), (C(∧)N. deprotonated 2-phenylpyridine; dppa. bis(diphenylphosphino)amine; dppm. bis(diphenylphosphino)methane) were suggested to have pentacoordinated geometry as investigated by NMR and conductometry. Pharmacological effects of 1 and 2 were evaluated for their proteasome-inhibitory and apoptosis-inducing activities under in vitro and in vivo conditions, showing significant proteasome-inhibitory activity against purified 20S proteasome, while 2 demonstrated superior inhibitory activity against cellular 26S proteasome. Consistently, this effect was associated with higher levels of proteasome target proteins and apoptosis induction in breast cancer cells. Importantly, preliminary studies show 1 and 2 were able to exert a similar effect in vivo by inhibiting the growth of breast cancer xenografts in mice, which was associated with proteasome inhibition and apoptosis induction. Interaction of 1 and 2 with herring sperm DNA was investigated by fluorimeteric emission, suggesting that Pt(II)-containing biphosphine complexes with DNA binding capabilities can also target and inhibit the tumor proteasome.
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Affiliation(s)
- Michael Frezza
- The Developmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute, and Departments of Oncology, Pharmacology and Pathology, School of Medicine, Wayne State University, Detroit, Michigan, USA
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Westendorf AF, Bodtke A, Bednarski PJ. Studies on the photoactivation of two cytotoxic trans,trans,trans-diazidodiaminodihydroxo-Pt(IV) complexes. Dalton Trans 2011; 40:5342-51. [PMID: 21461431 DOI: 10.1039/c0dt01485k] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Light-activation of metal ion complexes to cytotoxic species is of interest due to the potential use in anticancer therapy. Two platinum complexes, trans,trans,trans-[Pt(IV)(N(3))(2)(OH)(2)(NH(3))(2)] (3) and trans,trans,trans-[Pt(IV)(N(3))(2)(OH)(2)(py)(NH(3))] (4) were irradiated with either UV (λ = 366 nm) or white fluorescent light and the various photochemical and photobiological phenomena were characterized. HPLC coupled to UV/Vis and MS detection was used to identify photochemical species resulting from irradiation of 4 with UV and white light. These studies showed that various Pt(IV) and Pt(II) products formed during the photolysis. The mass spectra of Pt(IV) complexes showed Pt ions in both the positive as well as the negative mode while Pt(II) complexes resulted in only positively charged Pt(III) ions. Since cellular DNA is considered to be a key target for platinum antitumor drugs, the irreversible platination of calf thymus DNA by the photoactivated Pt(IV) complexes was followed by Atomic Adsorption spectrometry (AAS). The effect of adding chloride or biological reducing agents glutathione (GSH) and ascorbic acid on the rates of DNA platination where also studied. Upon activation by light, both compounds show similar binding behaviour to DNA, but the rates of DNA platination for 3 were faster than for 4. Both chloride and GSH protected DNA from platination by the photoactivated compounds; consistent with the trapping of reactive aqua-Pt species. The presence of ascorbate increased the level of platinum bound to DNA for photoactivated 4 but not for 3. Without photoactivation, little or no DNA platination was observed, either with or without ascorbate or GSH. Cytotoxicity studies with two human cancer cell lines underline the photochemotherapeutic potential of these compounds. Striking is the increase in cytotoxic potency with the replacement of an ammine by a pyridine ligand.
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Affiliation(s)
- Aron F Westendorf
- Pharmazeutische/Medizinische Chemie, Institut für Pharmazie, Ernst-Moritz-Arndt Universität Greifswald, 17487, Greifswald, Germany
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Sokolov AY, Schaefer III HF. Ground and excited state properties of photoactive platinum(iv) diazido complexes: Theoretical considerations. Dalton Trans 2011; 40:7571-82. [DOI: 10.1039/c1dt10493d] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Farrer NJ, Woods JA, Munk VP, Mackay FS, Sadler PJ. Photocytotoxic trans-diam(m)ine platinum(IV) diazido complexes more potent than their cis isomers. Chem Res Toxicol 2010; 23:413-21. [PMID: 19994893 PMCID: PMC2933822 DOI: 10.1021/tx900372p] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The photocytotoxicity of a series of anticancer trans-dihydroxido [Pt(N(3))(2)(OH)(2)(NH(3))(X)] (X = alkyl or aryl amine) platinum(IV) diazido complexes has been examined, and the influence of cis-trans isomerism has been investigated. A series of photoactivatable Pt(IV)-azido complexes has been synthesized: The synthesis, characterization, and photocytotoxicity of six mixed-ligand ammine/amine Pt(IV) diazido complexes, cis,trans,cis-[Pt(N(3))(2)(OH)(2)(NH(3))(X)] where X = propylamine (4c), butylamine (5c), or pentylamine (6c) and aromatic complexes where X = pyridine (7c), 2-methylpyridine (8c), or 3-methylpyridine (9c) are reported. Six all-trans isomers have also been studied where X = methylamine (2t), ethylamine (3t), 2-methylpyridine (8t), 4-methylpyridine (10t), 3-methylpyridine (9t), and 2-bromo-3-methylpyridine (11t). All of the complexes exhibit intense azide-to-Pt(IV) LMCT bands (ca. 290 nm for trans and ca. 260 nm for cis). When irradiated with UVA light (365 nm), the Pt(IV) complexes undergo photoreduction to Pt(II) species, as monitored by UV-vis spectroscopy. The trans isomers of complexes containing aliphatic or aromatic amines were more photocytotoxic than their cis isomers. One of the cis complexes (9c) was nonphotocytotoxic despite undergoing photoreduction. Substitution of NH(3) ligands by MeNH(2) or EtNH(2) results in more potent photocytotoxicity for the all-trans complexes. The complexes were all nontoxic toward human keratinocytes (HaCaT) and A2780 human ovarian cancer cells in the dark, apart from the 3-methylpyridine (9t), 2-bromo-3-methylpyridine (11t), and 4-methylpyridine (10t) derivatives.
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Affiliation(s)
- Nicola J. Farrer
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
| | - Julie A. Woods
- Photobiology Unit, Department of Dermatology, Ninewells Hospital, Dundee, DD1 9SY, UK
| | - Vivienne P. Munk
- School of Chemistry, The University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh, EH9 3JJ, UK
| | - F. S. Mackay
- School of Chemistry, The University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh, EH9 3JJ, UK
| | - Peter J. Sadler
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
- School of Chemistry, The University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh, EH9 3JJ, UK
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Farrer NJ, Salassa L, Sadler PJ. Photoactivated chemotherapy (PACT): the potential of excited-state d-block metals in medicine. Dalton Trans 2009:10690-701. [PMID: 20023896 PMCID: PMC2933824 DOI: 10.1039/b917753a] [Citation(s) in RCA: 379] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The fields of phototherapy and of inorganic chemotherapy both have long histories. Inorganic photoactivated chemotherapy (PACT) offers both temporal and spatial control over drug activation and has remarkable potential for the treatment of cancer. Following photoexcitation, a number of different decay pathways (both photophysical and photochemical) are available to a metal complex. These pathways can result in radiative energy release, loss of ligands or transfer of energy to another species, such as triplet oxygen. We discuss the features which need to be considered when developing a metal-based anticancer drug, and the common mechanisms by which the current complexes are believed to operate. We then provide a comprehensive overview of PACT developments for complexes of the different d-block metals for the treatment of cancer, detailing the more established areas concerning Ti, V, Cr, Mn, Re, Fe, Ru, Os, Co, Rh, Pt, and Cu and also highlighting areas where there is potential for greater exploration. Nanoparticles (Ag, Au) and quantum dots (Cd) are also discussed for their photothermal destructive potential. We also discuss the potential held in particular by mixed-metal systems and Ru complexes.
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Affiliation(s)
- Nicola J. Farrer
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
| | - Luca Salassa
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
| | - Peter J. Sadler
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
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Bruijnincx PCA, Sadler PJ. Controlling Platinum, Ruthenium and Osmium Reactivity for Anticancer Drug Design. ADVANCES IN INORGANIC CHEMISTRY 2009; 61:1-62. [PMID: 21258628 PMCID: PMC3024542 DOI: 10.1016/s0898-8838(09)00201-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | - Peter J. Sadler
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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Mackay FS, Farrer NJ, Salassa L, Tai HC, Deeth RJ, Moggach SA, Wood PA, Parsons S, Sadler PJ. Synthesis, characterisation and photochemistry of Pt(IV) pyridyl azido acetato complexes. Dalton Trans 2009:2315-25. [PMID: 19290364 PMCID: PMC2933821 DOI: 10.1039/b820550g] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pt(II) azido complexes [Pt(bpy)(N(3))(2)] (1), [Pt(phen)(N(3))(2)] (2) and trans-[Pt(N(3))(2)(py)(2)] (3) incorporating the bidentate diimine ligands 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) or the monodentate pyridine (py) respectively, have been synthesised from their chlorido precursors and characterised by X-ray crystallography; complex 3 shows significant deviation from square-planar geometry (N(3)-Pt-N(3) angle 146.7 degrees ) as a result of steric congestion at the Pt centre. The novel Pt(IV) complexes trans, cis-[Pt(bpy)(OAc)(2)(N(3))(2)] (), trans, cis-[Pt(phen)(OAc)(2)(N(3))(2)] (), trans, trans, trans-[Pt(OAc)(2)(N(3))(2)(py)(2)] (), were obtained from via oxidation with H(2)O(2) in acetic acid followed by reaction of the intermediate with acetic anhydride. Complexes 4-6 exhibit interesting structural and photochemical properties that were studied by X-ray, NMR and UV-vis spectroscopy and TD-DFT (time-dependent density functional theory). These Pt(IV) complexes exhibit greater absorption at longer wavelengths (epsilon = 9756 M(-1) cm(-1) at 315 nm for 4 ; epsilon = 796 M(-1) cm(-1) at 352 nm for 5 ; epsilon = 16900 M(-1) cm(-1) at 307 nm for 6 , in aqueous solution) than previously reported Pt(IV) azide complexes, due to the presence of aromatic amines, and 4-6 undergo photoactivation with both UVA (365 nm) and visible green light (514 nm). The UV-vis spectra of complexes 4-6 were calculated using TD-DFT; the nature of the transitions contributing to the UV-vis bands provide insight into the mechanism of production of the observed photoproducts. The UV-vis spectra of 1-3 were also simulated by computational methods and comparison between Pt(II) and Pt(IV) electronic and structural properties allowed further elucidation of the photochemistry of 4-6.
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Affiliation(s)
- Fiona S. Mackay
- School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Nicola J. Farrer
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Luca Salassa
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Hui-Chung Tai
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Robert J. Deeth
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Stephen A. Moggach
- School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Peter A. Wood
- School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Simon Parsons
- School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Peter J. Sadler
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
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