1
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Matlou ML, Malan FP, Nkadimeng S, McGaw L, Tembu VJ, Manicum ALE. Exploring the in vitro anticancer activities of Re(I) picolinic acid and its fluorinated complex derivatives on lung cancer cells: a structural study. J Biol Inorg Chem 2023; 28:29-41. [PMID: 36463538 DOI: 10.1007/s00775-022-01971-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/04/2022] [Indexed: 12/07/2022]
Abstract
Fifteen rhenium(I) tricarbonyl complexes of the form fac-[Re(N,O')(CO)3(X)], where N,O'-bidentate ligand = 2-picolinic acid (Pico); 3,5-difluoropyridine-2-carboxylic acid (Dfpc); 3-trifluoromethyl-pyridine-2-carboxylic acid (Tfpc) and X = H2O; pyrazole (Pz); pyridine (Py); imidazole (Im); and methanol (CH3OH) were synthesized using the '2 + 1' mixed ligand approach with an average yield of 84%. The complexes were characterized using the following spectroscopic techniques: IR, 1H and 13C NMR, UV/Vis, and single-crystal X-ray diffraction. The effect of the fluorine atoms on the backbone of the N,O'-bidentate ligand was investigated and a trend was noticed in the carbonyl stretching frequencies: with Pico < Tfpc < Dfpc. The in vitro biological screening on Vero (healthy mammalian), HeLa (cervical carcinoma) and A549 (lung cancer) cells revealed one toxic complex, fac-[Re(Pico)(CO)3(H2O)], with respective LC50 values of 9.0 ± 0.9, 15.8 ± 4.9 (SI = 0.570) and 20.9 ± 0.8 (SI = 0.430) μg/mL. As a result, it can be used as a positive control drug of toxicity.
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Affiliation(s)
- Mabu L Matlou
- Department of Chemistry, Tshwane University of Technology, P.O. Box X680, Pretoria, 0001, South Africa
| | - Frederick P Malan
- Department of Chemistry, University of Pretoria, 02 Lynnwood Road, Hatfield, Pretoria, 0001, South Africa
| | - Sanah Nkadimeng
- Department of Life and Consumer Sciences, University of South Africa, Private Bag X6, Florida Campus, Florida, 1710, South Africa
| | - Lyndy McGaw
- Phytomedicine Programme, Department of Paraclinical Sciences, University of Pretoria, Private Bag X04, Onderstepoort, 0110, South Africa
| | - Vuyelwa J Tembu
- Department of Chemistry, Tshwane University of Technology, P.O. Box X680, Pretoria, 0001, South Africa
| | - Amanda-Lee E Manicum
- Department of Chemistry, Tshwane University of Technology, P.O. Box X680, Pretoria, 0001, South Africa.
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2
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Sidorenko GV, Miroslavov AE, Tyupina MY. Technetium(I) carbonyl complexes for nuclear medicine: Coordination-chemical aspect. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.214911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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3
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Synthesis and Characterization of Novel [2 + 1] Tricarbonyl Rhenium Complexes with the Hydrophilic Phosphine Ligands PTA and CAP. Bioinorg Chem Appl 2022; 2022:3117661. [PMID: 35734344 PMCID: PMC9208990 DOI: 10.1155/2022/3117661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 05/05/2022] [Accepted: 05/18/2022] [Indexed: 11/23/2022] Open
Abstract
In the pursuit of hydrophilic model fac-[Re(CO)3]+ complexes for (radio) pharmaceutical applications, six novel [2 + 1] mixed-ligand complexes of the general type fac-[Re(CO)3(bid)P] were synthesized and characterized, where bid is a bidentate ligand bearing either (N, O) or (S, S′) donor atom sets and P is the hydrophilic phosphine 1,3,5-triaza-7-phosphoadamantane (PTA) or its macrocyclic homologue 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP). The (N, O) ligands used in this study were picolinic and quinaldic acid, while the (S, S′) ligand was diethyldithiocarbamate. The complexes were synthesized in generally high yields and purity and the characterization was performed by spectroscopic methods, IR, NMR, and elemental analysis. Detailed X-ray crystallographic study of molecular packing by using Hirshfeld analysis tools revealed a plethora of intermolecular interactions such as hydrogen bond, π⋯π, C-H⋯π, and carbonyl-carbonyl interactions. To our knowledge, the CAP complexes reported herein are the first example of [2 + 1] mixed-ligand fac-[Re(CO)3]+ complexes with CAP. The new complexes might have the potential to serve as platforms for the design of target-specific complexes with favorable pharmacokinetics.
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Cooper SM, White AJP, Eykyn TR, Ma MT, Miller PW, Long NJ. N-Centered Tripodal Phosphine Re(V) and Tc(V) Oxo Complexes: Revisiting a [3 + 2] Mixed-Ligand Approach. Inorg Chem 2022; 61:8000-8014. [PMID: 35544683 PMCID: PMC9131457 DOI: 10.1021/acs.inorgchem.2c00693] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
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N-Triphos derivatives
(NP3R, R = alkyl, aryl)
and asymmetric variants (NP2RXR′, R′ = alkyl, aryl, X = OH, NR2, NRR′) are
an underexplored class of tuneable, tripodal ligands in relation to
the coordination chemistry of Re and Tc for biomedical applications.
Mixed-ligand approaches are a flexible synthetic route to obtain Tc
complexes of differing core structures and physicochemical properties.
Reaction of the NP3Ph ligand with the Re(V)
oxo precursor [ReOCl3(PPh3)2] generated
the bidentate complex [ReOCl3(κ2-NP2PhOHAr)], which possesses an unusual
AA’BB’XX’ spin system with a characteristic second-order
NMR lineshape that is sensitive to the bi- or tridentate nature of
the coordinating diphosphine unit. The use of the asymmetric NP2PhOHAr ligand resulted in the formation
of both bidentate and tridentate products depending on the presence
of base. The tridentate Re(V) complex [ReOCl2(κ3-NP2PhOAr)] has provided
the basis of a new reactive “metal-fragment” for further
functionalization in [3 + 2] mixed-ligand complexes. The synthesis
of [3 + 2] complexes with catechol-based π-donors could also
be achieved under one-pot, single-step conditions from Re(V) oxo precursors.
Analogous complexes can also be synthesized from suitable 99Tc(V) precursors, and these complexes have been shown to exhibit
highly similar structural properties through spectroscopic and chromatographic
analysis. However, a tendency for the {MVO}3+ core to undergo hydrolysis to the {MVO2}+ core has been observed both in the case of M = Re and markedly
for M = 99Tc complexes. It is likely that controlling this
pathway will be critical to the generation of further stable Tc(V)
derivatives. An N-centered tripodal heterofunctionalized
phosphine ligand
was used to generate a reactive “metal-fragment” based
on the {MVO}3+ (M = Re, 99Tc) core
for the formation of mixed-ligand [3 + 2] complexes. Characteristic
lineshapes arising from an AA’BB’XX’ spin system
are diagnostic of bidentate vs tridentate coordination modes of the
ligand.
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Affiliation(s)
- Saul M Cooper
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, 82 Wood Lane, White City Campus, London W12 0BZ, UK.,School of Biomedical Engineering & Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London SE1 7EH, UK
| | - Andrew J P White
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, 82 Wood Lane, White City Campus, London W12 0BZ, UK
| | - Thomas R Eykyn
- School of Biomedical Engineering & Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London SE1 7EH, UK
| | - Michelle T Ma
- School of Biomedical Engineering & Imaging Sciences, King's College London, 4th Floor Lambeth Wing, St Thomas' Hospital, London SE1 7EH, UK
| | - Philip W Miller
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, 82 Wood Lane, White City Campus, London W12 0BZ, UK
| | - Nicholas J Long
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, 82 Wood Lane, White City Campus, London W12 0BZ, UK
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Schindler K, Zobi F. Anticancer and Antibiotic Rhenium Tri- and Dicarbonyl Complexes: Current Research and Future Perspectives. Molecules 2022; 27:539. [PMID: 35056856 PMCID: PMC8777860 DOI: 10.3390/molecules27020539] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 12/23/2021] [Accepted: 01/12/2022] [Indexed: 12/20/2022] Open
Abstract
Organometallic compounds are increasingly recognized as promising anticancer and antibiotic drug candidates. Among the transition metal ions investigated for these purposes, rhenium occupies a special role. Its tri- and dicarbonyl complexes, in particular, attract continuous attention due to their relative ease of preparation, stability and unique photophysical and luminescent properties that allow the combination of diagnostic and therapeutic purposes, thereby permitting, e.g., molecules to be tracked within cells. In this review, we discuss the anticancer and antibiotic properties of rhenium tri- and dicarbonyl complexes described in the last seven years, mainly in terms of their structural variations and in vitro efficacy. Given the abundant literature available, the focus is initially directed on tricarbonyl complexes of rhenium. Dicarbonyl species of the metal ion, which are slowly gaining momentum, are discussed in the second part in terms of future perspective for the possible developments in the field.
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Affiliation(s)
| | - Fabio Zobi
- Department of Chemistry, Fribourg University, Chemin du Musée 9, 1700 Fribourg, Switzerland;
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Lazopoulos A, Triantis C, Shegani A, Papasavva A, Raptopoulou CP, Psycharis V, Chiotellis A, Pelecanou M, Pirmettis I, Papadopoulos MS. Effective Labeling of Amine Pharmacophores through the Employment of 2,3-Pyrazinedicarboxylic Anhydride and the Generation of fac-[M(CO) 3(PyA)P] and cis-trans-[M(CO) 2(PyA)P 2] Complexes (PyA = Pyrazine-2-carboxylate, P = Phosphine, M = Re, 99mTc). Inorg Chem 2021; 60:17509-17516. [PMID: 34788019 DOI: 10.1021/acs.inorgchem.1c01968] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The fac-[M(CO)3(PyA)(P)] and cis-trans-[M(CO)2(PyA)(P)2] neutral complexes (M is Re or 99mTc), based on the mixed ligand strategy with pyrazine-2-carboxylic acid (PyAH) as the bidentate N,O and triphenylphosphine as the monodentate P ligand, are presented. Through the employment of the anhydride of pyrazine-2,3-dicarboxylic acid (PyDA), the PyAH scaffold was conveniently derivatized with the model bioactive amine 1-(2-methoxyphenyl)piperazine, the active part of the 5-HT1A antagonist WAY100635. Reaction of either PyAH or the pharmacophore-bearing PyAH ligand (L1H) with fac-[M(CO)3]+ core in water yielded the intermediate fac-[M(CO)3(PyA)(H2O)] complexes. The labile aqua ligand was easily replaced by PPh3 to yield the fac-[Re(CO)3(PyA)(PPh3)] complexes, while in toluene under reflux, the cis-trans-[Re(CO)2(PyA)(PPh3)2] complexes were obtained. The latter complexes were alternatively obtained from mer-[Re(CO)3(PPh3)2Cl] by refluxing with the PyA ligand in toluene. The analogous 99mTc complexes were synthesized quantitatively, showing excellent stability in competition studies. The methodology described herein represents a practical procedure for the effective integration of the fac-[M(CO)3]+ core with amine-bearing biologically active compounds for diagnosis/therapy.
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Priyatharsini M, Mishra I, Shankar B, Srinivasan N, Krishnakumar RV, Sathiyendiran M. fac-Re(CO)3 core-based complex featuring benzimidazole as pendant motif from hydroxyquinoline and pyridylbenzimidazole. J Organomet Chem 2021. [DOI: 10.1016/j.jorganchem.2021.122052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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8
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Shegani A, Ischyropoulou M, Roupa I, Kiritsis C, Makrypidi K, Papasavva A, Raptopoulou C, Psycharis V, Hennkens HM, Pelecanou M, Papadopoulos MS, Pirmettis I. Synthesis and evaluation of new mixed "2 + 1" Re, 99mTc and 186Re tricarbonyl dithiocarbamate complexes with different monodentate ligands. Bioorg Med Chem 2021; 47:116373. [PMID: 34467870 DOI: 10.1016/j.bmc.2021.116373] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 11/24/2022]
Abstract
A series of "2 + 1" mixed ligand tricarbonyl complexes of the general formula fac-[Re/99mTc/186Re(CO)3(DDTC)(L)] containing diethyldithiocarbamate (DDTC) as a monoanionic bidentate ligand and a series of monodentate ligands L was synthesized, characterized and evaluated. The impact of ligand L on the radiochemical yield (RCY) and biodistribution of the final compounds was also investigated. DDTC and the appropriate L ligand [cyclohexyl isocyanide (cisc), tert-butyl isocyanide (tbi), triphenylphosphine (PPh3), methyldiphenylphosphine (PPh2Me), triphenylarsine (AsPh3), imidazole (im), and 4-aminopyridine (4AP)] readily reacted in equimolar amounts with the [Et4N]2[Re(CO)3Br3] precursor to afford fac-[Re(CO)3(DDTC)(cisc)], Re1, fac-[Re(CO)3(DDTC)(tbi)], Re2, fac-[Re(CO)3(DDTC)(PPh3)], Re3, fac-[Re(CO)3(DDTC)(PPh2Me)], Re4, fac-[Re(CO)3(DDTC)(AsPh3)], Re5, fac-[Re(CO)3(DDTC)(im)], Re6 and fac-[Re(CO)3(DDTC)(4AP)], Re7, complexes in high yields (>80%). All Re complexes were fully characterized by IR, NMR, and in addition Re4, Re5, and Re7 with X-ray crystallography. Analogous reactions as performed with Re were subsequently explored on the 99mTc and 186Re-tracer levels using the corresponding fac-[99mTc/186Re(CO)3(H2O)3]+ precursor. Complexes 99mTc1 - 99mTc5, 186Re1 and 186Re3 were obtained in high radiochemical yield (>91%), while the complexes 99mTc6, 99mTc7 and 186Re7 formed with radiochemical yields of 55%, 28%, and 75%, respectively. The 99mTc and 186Re-complexes were characterized by comparative HPLC analysis using the analogous Re complexes. During histidine and cysteine challenge experiments at 37 °C through 6 h, complexes 99mTc1 - 99mTc5 remained > 92% stable, while complexes 99mTc6 and 99mTc7 remained only 8% stable through 3 h. Similar studies for 186Re-complexes showed that 186Re1 and 186Re3 remained > 95% stable for up to 48 h, while 186Re7 had decreased to 7% after 3 h. LogD7.4 data of 99mTc1 - 99mTc5, 186Re1, and 186Re3 complexes, which ranged from 2.59 to 3.39, suggested high lipophilicity. Biodistribution studies in healthy Swiss albino mice showed hepatobiliary excretion for 99mTc1, 99mTc2, and 99mTc4, fast blood clearance for 99mTc4, while high liver uptake and retention for 99mTc3 and 99mTc5 were measured. Moreover, 99mTc2 showed high accumulation in the lungs with sustained retention (52.80% ID/g at 4 h p.i.) and significant brain uptake at 2 min p.i. (1.89% ID/g). The study showed the great influence of monodentate ligand in the synthesis and biodistribution of the mixed ligand complexes.
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Affiliation(s)
- Antonio Shegani
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece; Research Reactor Center, University of Missouri, Columbia, MO 65211, United States
| | - Myrto Ischyropoulou
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Ioanna Roupa
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Christos Kiritsis
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Konstantina Makrypidi
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Afroditi Papasavva
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Catherine Raptopoulou
- Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Vassilis Psycharis
- Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Heather M Hennkens
- Research Reactor Center, University of Missouri, Columbia, MO 65211, United States; Department of Chemistry, University of Missouri, Columbia, MO 65211, United States
| | - Maria Pelecanou
- Institute of Biosciences & Applications, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Minas S Papadopoulos
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
| | - Ioannis Pirmettis
- Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15310 Athens, Greece.
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Schindler K, Crochet A, Zobi F. Aerobically stable and substitutionally labile α-diimine rhenium dicarbonyl complexes. RSC Adv 2021; 11:7511-7520. [PMID: 35423250 PMCID: PMC8694950 DOI: 10.1039/d1ra00514f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 02/05/2021] [Indexed: 12/11/2022] Open
Abstract
New synthetic routes to aerobically stable and substitutionally labile α-diimine rhenium(i) dicarbonyl complexes are described. The molecules are prepared in high yield from the cis–cis–trans-[Re(CO)2(tBu2bpy)Br2]− anion (2, where tBu2bpy is 4,4′-di-tert-butyl-2,2′-bipyridine), which can be isolated from the one electron reduction of the corresponding 17-electron complex (1). Compound 2 is stable in the solid state, but in solution it is oxidized by molecular oxygen back to 1. Replacement of a single bromide of 2 by σ-donor monodentate ligands (Ls) yields stable neutral 18-electron cis–cis–trans-[Re(CO)2(tBu2bpy)Br(L)] species. In coordinating solvents like methanol the halide is replaced giving the corresponding solvated cations. [Re(CO)2(tBu2bpy)Br(L)] species can be further reacted with Ls to prepare stable cis–cis–trans-[Re(CO)2(tBu2bpy)(L)2]+ complexes in good yield. Ligand substitution of Re(i) complexes proceeds via pentacoordinate intermediates capable of Berry pseudorotation. In addition to the cis–cis–trans-complexes, cis–cis–cis- (all cis) isomers are also formed. In particular, cis–cis–trans-[Re(CO)2(tBu2bpy)(L)2]+ complexes establish an equilibrium with all cis isomers in solution. The solid state crystal structure of nearly all molecules presented could be elucidated. The molecules adopt a slightly distorted octahedral geometry. In comparison to similar fac-[Re(CO)3]+complexes, Re(i) diacarbonyl species are characterized by a bend (ca. 7°) of the axial ligands towards the α-diimine unit. [Re(CO)2(tBu2bpy)Br2]− and [Re(CO)2(tBu2bpy)Br(L)] complexes may be considered as synthons for the preparation of a variety of new stable diamagnetic dicarbonyl rhenium cis-[Re(CO)2]+ complexes, offering a convenient entry in the chemistry of the core. New synthetic routes to aerobically stable and substitutionally labile α-diimine rhenium(i) dicarbonyl complexes offer a convenient entry in the chemistry of the cis-[Re(CO)2]+ core.![]()
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Affiliation(s)
- Kevin Schindler
- Department of Chemistry, Fribourg University Chemin Du Musée 9 1700 Fribourg Switzerland
| | - Aurélien Crochet
- Department of Chemistry, Fribourg University Chemin Du Musée 9 1700 Fribourg Switzerland
| | - Fabio Zobi
- Department of Chemistry, Fribourg University Chemin Du Musée 9 1700 Fribourg Switzerland
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The first use of tri(1-naphthyl)phosphine oxide as ligand for rhenium(I)- complexes from phosphine via a one-pot approach. J Organomet Chem 2021. [DOI: 10.1016/j.jorganchem.2020.121657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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11
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Vogler A, Hischa B, Stempfhuber S. Synthesis, crystal structure and photoluminescence of [NHEt 3][Re(I)(quinaldate)(CO) 3Cl]. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2019. [DOI: 10.1515/znb-2019-0066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The salt [NHEt3][Re(I)(quinaldate)(CO)3Cl] was obtained by the reaction of Re(CO)5Cl with quinaldic acid and triethylamine in toluene. The crystal structure analysis of this salt revealed the presence of the complex anion [Re(quinaldate)(CO)3Cl]−, with the d
6 Re(I) metal center in a pseudo-octahedral environment. The electronic spectra in absorption and emission exhibit bands which are attributed to quinaldate IL and CT transitions at comparable energies. The longest-wavelength emission originates from a Re(I) to quinaldate MLCT triplet, which can be quenched in solution by oxygen or triethylamine.
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Affiliation(s)
- Arnd Vogler
- Institute of Inorganic Chemistry , University of Regensburg , Universitätsstraße 31 , 93053 Regensburg , Germany
| | - Birgit Hischa
- X-ray Central Analytics , University of Regensburg , Universitätsstraße 31 , 93053 Regensburg , Germany
| | - Sabine Stempfhuber
- X-ray Central Analytics , University of Regensburg , Universitätsstraße 31 , 93053 Regensburg , Germany
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