Insights into the cytotoxic activity of the phosphane copper(I) complex [Cu(thp)4][PF6]

Synthesis and Investigations of the Antitumor Effects of First-Row Transition Metal(II) Complexes Supported by Two Fluorinated and Non-Fluorinated β-Diketonates

The 3d transition metal (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes, supported by anions of sterically demanding β-diketones, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3), were synthesized and evaluated for their antitumor activity. To assess the biological effects of substituents on phenyl moieties, we also synthesized and investigated the analogous metal(II) complexes of the anion of the less bulky 1,3-diphenylpropane-1,3-dione (HLPh) ligand. The compounds [Cu(LCF3)2], [Cu(LMes)2] and ([Zn(LMes)2]) were characterized by X-ray crystallography. The [Cu(LCF3)2] crystallizes with an apical molecule of solvent (THF) and features a rare square pyramidal geometry at the Cu(II) center. The copper(II) and zinc(II) complexes of diketonate ligands, derived from the deprotonated 1,3-dimesitylpropane-1,3-dione (HLMes), adopt a square planar or a tetrahedral geometry at the metal, respectively. We evaluated the antitumor properties of the newly synthesized (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes against a series of human tumor cell lines derived from different solid tumors. Except for iron derivatives, cellular studies revealed noteworthy antitumor properties, even towards cancer cells endowed with poor sensitivity to the reference drug cisplatin.

New Copper Complexes with N,O-Donor Ligands Based on Pyrazole Moieties Supported by 3-Substituted Acetylacetone Scaffolds

The new 3-monosubstituted acetylacetone ligands, 3-(phenyl(1H-pyrazol-1-yl)methyl)pentane-2,4-dione (HLacPz) and 3-((3,5-dimethyl-1H-pyrazol-1-yl)(phenyl)methyl)pentane-2,4-dione (HLacPzMe), were synthesized and used as supporting ligands for new copper(II) and copper(I) phosphane complexes of the general formulae [Cu(HLacX)2(LacX)2] and [Cu(PPh3)2(HLacX)]PF6 (X = Pz (pyrazole) or PzMe (3,5-dimethylpyrazole)), respectively. In the syntheses of the Cu(I) complexes, the triphenylphosphine coligand (PPh3) was used to stabilize copper in the +1 oxidation state, avoiding oxidation to Cu(II). All compounds were characterized by CHN analysis, 1H-NMR, 13C-NMR, FT-IR spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). The ligands HLacPz (1) and HLacPzMe (2) and the copper complex [Cu(PPh3)2(HLacPz)]PF6 (3) were also characterized by X-ray crystallography. The reactivity of these new compounds was investigated and the new compounds 4-phenyl-4-(1H-pyrazol-1-yl)butan-2-one (7) and 4-(3,5-dimethyl-1H-pyrazol-1-yl)-4-phenylbutan-2-one (8) were obtained in basic conditions via the retro-Claisen reaction of related 3-monosubstituted acetylacetone, providing efficient access to synthetically useful ketone compounds. Compound 8 was also characterized by X-ray crystallography.

A binuclear Cu(I)-phosphine complex as a specific HSA site I binder: synthesis, X-ray structure determination, and a comprehensive HSA interaction analysis

In this research, we present a method for synthesis and a detailed description of geometry characterization of a novel binuclear Cu(I) phosphine complex, along with analysis of its interaction with HSA using spectroscopic and simulation methods. The Cu atoms are coordinated in a tetrahedral geometry, which results in coordination by two nitrogen atoms from the N,N'-(ethane-1,2-diyl)bis(1-(pyridin-2-yl)methanimine ligand (L), a chloride, and a PPh3. The complex binding constant to HSA in a biochemical environment was determined to be ∼106, which is indicative of a strong interaction. The fluorescence of HSA is significantly quenched by binding to the complex via a static mechanism, whereas the microenvironment of the tryptophan residue remains unchanged. A spontaneous binding process was indicated by a negative value for ΔG. Thermodynamic signatures reflect the dominance of hydrophobic forces during the interaction. The site marker competitive experiment combined with docking simulation analysis revealed the closeness position of the complex binding site to warfarin location in specific ligand site I of HSA. The information generated in the present study would be valuable to understand the interaction mechanistic and pharmacological behavior of Cu(I) complexes.Communicated by Ramaswamy H. Sarma.

Synthesis and cytotoxicity studies of Cu(I) and Ag(I) complexes based on sterically hindered β-diketonates with different degrees of fluorination

Design, synthesis, and in vitro antitumor properties of Cu(I) and Ag(I) phosphane complexes supported by the anions of sterically hindered β-diketone ligands, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3) featuring trifluoromethyl or methyl groups on the phenyl moieties have been reported. In order to compare the biological effects of substituents on the phenyl moieties, the analogous copper(I) and silver(I) complexes of the anion of the parent 1,3-diphenylpropane-1,3-dione (HLPh) ligand were also synthesized and included in the study. In the syntheses of the Cu(I) and Ag(I) complexes, the phosphane coligands triphenylphosphine (PPh3) and 1,3,5-triaza-7-phosphaadamantane (PTA) were used to stabilize silver and copper in the +1 oxidation state, preventing the metal ion reduction to Ag(0) or oxidation to Cu(II), respectively. X-ray crystal structures of HLCF3 and the metal adducts [Cu(LCF3)(PPh3)2] and [Ag(LPh)(PPh3)2] are also presented. The antitumor properties of both classes of metal complexes were evaluated against a series of human tumor cell lines derived from different solid tumors, by means of both 2D and 3D cell viability studies. They display noteworthy antitumor properties and are more potent than cisplatin in inhibiting cancer cell growth.

Cu(I) complexes as new antiproliferative agents against sensitive and doxorubicin resistant colorectal cancer cells: synthesis, characterization, and mechanisms of action

Cancer is one of the worst health issues worldwide, representing the second leading cause of death. Current chemotherapeutic drugs face some challenges like the acquired resistance of the tumoral cells and low specificity leading to unwanted side effects. There is an urgent need to develop new compounds that may target resistant cells. The synthesis and characterization of two Cu(i) complexes of general formula [Cu(PP)(LL)][BF4], where PP is a phosphane ligand (triphenylphosphine or 1,2-bis(diphenylphosphano) ethane) and LL = is a heteroaromatic bidentate ligand (4,4'-dimethyl-2,2'-bipyridine and 6,3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). The new compounds were fully characterized by spectroscopic techniques (NMR, FTIR and UV-vis.), elemental analysis (C, H, N and S) and two structures were determined by single X-ray diffraction studies. The antiproliferative potential of the new Cu(i) complexes were studied in tumor (breast adenocarcinoma, ovarian carcinoma and in colorectal carcinoma sensitive and resistant to doxorubicin) and normal (fibroblasts) cell lines. Complexes 1-4 did not show any antiproliferative potential. Amongst the complexes 5-8, complex 8 shows high cytotoxic potential against colorectal cancer sensitive and resistant to doxorubicin and low cytotoxicity towards healthy cells. We show that complexes 5-8 can cleave pDNA and, in particular, the in vitro pDNA cleavage is due to an oxidative mechanism. This oxidative mechanism corroborates the induction of reactive oxygen species (ROS), that triggers HCT116 cell death via apoptosis, as proved by the increased expression of BAX protein relative to BCL-2 protein and the depolarization of mitochondrial membrane potential, and via autophagy. Additionally, complex 8 can block the cell cycle in the G1 phase, also exhibiting a cytostatic potential. Proteomic analysis confirmed the apoptotic, autophagic and cytostatic potential of complex 8, as well as its ability to produce ROS and cause DNA damage. The interference of the complex in folding and protein synthesis and its ability to cause post-translational modifications was also verified. Finally, it was observed that the complex causes a reduction in cellular metabolism. The results herein demonstrated the potential of Cu(i) complexes in targeting doxorubicin sensitive and resistant cells which is positive and must be further explored using in vivo animal models.

Antiproliferative Homoleptic and Heteroleptic Phosphino Silver(I) Complexes: Effect of Ligand Combination on Their Biological Mechanism of Action

A series of neutral mixed-ligand [HB(pz)₃]Ag(PR₃) silver(I) complexes (PR₃ = tertiary phosphine, [HB(pz)₃]⁻ = tris(pyrazolyl)borate anion), and the corresponding homoleptic [Ag(PR₃)₄]BF₄ compounds have been synthesized and fully characterized. Silver compounds were screened for their antiproliferative activities against a wide panel of human cancer cells derived from solid tumors and endowed with different platinum drug sensitivity. Mixed-ligand complexes were generally more effective than the corresponding homoleptic derivatives, but the most active compounds were [HB(pz)₃]Ag(PPh₃) (5) and [Ag(PPh₃)₄]BF₄ (10), both comprising the lipophilic PPh₃ phosphine ligand. Detailed mechanistic studies revealed that both homoleptic and heteroleptic silver complexes strongly and selectively inhibit the selenoenzyme thioredoxin reductase both as isolated enzyme and in human ovarian cancer cells (half inhibition concentration values in the nanomolar range) causing the disruption of cellular thiol-redox homeostasis, and leading to apoptotic cell death. Moreover, for heteroleptic Ag(I) derivatives, an additional ability to damage nuclear DNA has been detected. These results confirm the importance of the type of silver ion coordinating ligands in affecting the biological behavior of the overall corresponding silver complexes, besides in terms of hydrophilic–lipophilic balance, also in terms of biological mechanism of action, such as interaction with DNA and/or thioredoxin reductase.

New copper(I) complexes selective for prostate cancer cells

A new family of eighteen Cu(i) complexes of the general formula [Cu(PP)(LL)][BF4], where PP is a phosphane ligand and LL represents an N,O-heteroaromatic bidentate ligand, has been synthesized and fully characterized by classical analytical and spectroscopic methods. Five complexes of this series were also characterized by single crystal X-ray diffraction studies. The cytotoxicity of all compounds was evaluated in breast (MCF7) and prostate (LNCap) human cancer cells and in a normal prostate cell line (RWPE). In general, all compounds showed higher cytotoxicity for the prostate cancer cells than for the breast cells, with IC50 values in the range 0.2-2 μM after 24 h of treatment. The most cytotoxic compound, [Cu(dppe)(2-ap)][BF4] (16), where dppe = 1,2-bis(diphenylphosphano) ethane and 2-ap = 2-acetylpyridine, showed a high level of cellular internalization, generation of intracellular ROS and activation of the cell death mechanism via apoptosis/necrosis. Owing to its high cytotoxic activity for LNCap cells, being 70-fold higher than that for normal prostate cells (RWPE), complex (16) was found to be the most promising for further research in prostate cancer models.

Detailing the Self-Discharge of a Cathode Based on a Prussian Blue Analogue

Prussian Blue analogues (PBAs) are a promising class of electrode active materials for batteries. Among them, copper nitroprusside, Cu[Fe(CN)5NO], has recently been investigated for its peculiar redox system, which also involves the nitrosyl ligand as a non-innocent ligand, in addition to the electroactivity of the metal sites, Cu and Fe. This paper studies the dynamics of the electrode, employing surface sensitive X-ray Photoelectron spectroscopy (XPS) and bulk sensitive X-ray absorption spectroscopy (XAS) techniques. XPS provided chemical information on the layers formed on electrode surfaces following the self-discharge process of the cathode material in the presence of the electrolyte. These layers consist mainly of electrolyte degradation products, such as LiF, LixPOyFz and LixPFy. Moreover, as evidenced by XAS and XPS, reduction at both metal sites takes place in the bulk and in the surface of the material, clearly evidencing that a self-discharge process is occurring. We observed faster processes and higher amounts of reduced species and decomposition products in the case of samples with a higher amount of coordination water.

Highly Hydrophilic Gold Nanoparticles as Carrier for Anticancer Copper(I) Complexes: Loading and Release Studies for Biomedical Applications

Gold nanoparticles (AuNPs), which are strongly hydrophilic and dimensionally suitable for drug delivery, were used in loading and release studies of two different copper(I)-based antitumor complexes, namely [Cu(PTA)4]+ [BF4]- (A; PTA = 1, 3, 5-triaza-7-phosphadamantane) and [HB(pz)3Cu(PCN)] (B; HB(pz)3 = tris(pyrazolyl)borate, PCN = tris(cyanoethyl)phosphane). In the homoleptic, water-soluble compound A, the metal is tetrahedrally arranged in a cationic moiety. Compound B is instead a mixed-ligand (scorpionate/phosphane), neutral complex insoluble in water. In this work, the loading procedures and the loading efficiency of A and B complexes on the AuNPs were investigated, with the aim to improve their bioavailability and to obtain a controlled release. The non-covalent interactions of A and B with the AuNPs surface were studied by means of dynamic light scattering (DLS), UV-Vis, FT-IR and high-resolution x-ray photoelectron spectroscopy (HR-XPS) measurements. As a result, the AuNPs-A system proved to be more stable and efficient than the AuNPs-B system. In fact, for AuNPs-A the drug loading reached 90%, whereas for AuNPs-B it reached 65%. For AuNPs-A conjugated systems, a release study in water solution was performed over 4 days, showing a slow release up to 10%.

Direct label-free imaging of brain tissue using synchrotron light: a review of new spectroscopic tools for the modern neuroscientist

The incidence of brain disease and brain disorders is increasing on a global scale. Unfortunately, development of new therapeutic strategies has not increased at the same rate, and brain diseases and brain disorders now inflict substantial health and economic impacts. A greater understanding of the fundamental neurochemistry that underlies healthy brain function, and the chemical pathways that manifest in brain damage or malfunction, are required to enable and accelerate therapeutic development. A previous limitation to the study of brain function and malfunction has been the limited number of techniques that provide both a wealth of biochemical information, and spatially resolved information (i.e., there was a previous lack of techniques that provided direct biochemical or elemental imaging at the cellular level). In recent times, a suite of direct spectroscopic imaging techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence microscopy (XFM), and X-ray absorption spectroscopy (XAS) have been adapted, optimized and integrated into the field of neuroscience, to fill the above mentioned capability-gap. Advancements at synchrotron light sources, such as improved light intensity/flux, increased detector sensitivities and new capabilities of imaging/optics, has pushed the above suite of techniques beyond "proof-of-concept" studies, to routine application to study complex research problems in the field of neuroscience (and other scientific disciplines). This review examines several of the major advancements that have occurred over the last several years, with respect to FTIR, XFM and XAS capabilities at synchrotron facilities, and how the increases in technical capabilities have being integrated and used in the field of neuroscience.

New Copper Compounds with Antiplatelet Aggregation Activity

BACKGROUND

Ischemic heart disease, cerebrovascular accident, and venous thromboembolism have the presence of a thrombotic event in common and represent the most common causes of death within the population.

OBJECTIVE

Since Schiff base copper(II) complexes are able to interact with polyphosphates (PolyP), a procoagulant and potentially prothrombotic platelet agent, we investigated the antiplatelet aggregating properties of two novel tridentate Schiff base ligands and their corresponding copper( II) complexes.

METHODS

The Schiff base ligands (L1) and (L2), as well as their corresponding copper(II) complexes (C1) and (C2), were synthesized and characterized by chemical analysis, X-ray diffraction, mass spectrometry, and UV-Visible, IR and far IR spectroscopy. In addition, EPR studies were carried out for (C1) and (C2), while (L1) and (L2) were further analyzed by 1H and 13C NMR. Tests for antiplatelet aggregation activities of all of the four compounds were conducted.

RESULTS

X-ray diffraction studies show that (L1) and (L2) exist in the enol-imine tautomeric form with a strong intramolecular hydrogen bond. NMR studies show that both ligands are found as enol-imine tautomers in CDCl3 solution. In the solid state, the geometry around the copper(II) ion in both (C1) and (C2) is square planar. EPR spectra suggest that the geometry of the complexes is similar to that observed in the solid state by X-ray crystallography. Compound (C2) exhibited the strongest antiplatelet aggregation activity.

CONCLUSION

Schiff base copper(II) complexes, which are attracting increasing interest, could represent a new approach to treat thrombosis by blocking the activity of PolyP with a potential anticoagulant activity and, most importantly, demonstrating no adverse bleeding events.

Coordinative unsaturated CuI entities are crucial intermediates governing cell internalization of copper. A combined experimental ESI-MS and DFT study

Model peptides relevant to hCtr1 transchelate Cu^I from the anti-tumour [Cu^I(PTA)₄]⁺ complex before metal internalization into tumor cells.

Thermodynamic stability and structure in aqueous solution of the [Cu(PTA)4]+ complex (PTA = aminophosphine‑1,3,5‑triaza‑7‑phosphaadamantane)

The chemistry of copper(I) with water-soluble phosphines is an emergent area of study which has the objective of finding ligands that stabilize copper in its lower oxidation state. Cu(I) has been found relevant in the mechanism of copper transports into cells, and the accessibility of this oxidation state has implications in oxidative stress processes. For these reasons the possibility to deal with stable, water soluble copper(I) is an attractive approach for devising new biologically relevant metal-based drugs and chelating agents. Here we present the X-ray absorption spectroscopy (XAS) and UV-visible spectrophotometric study of the [Cu(PTA)₄]BF₄ complex (PTA = aminophosphine‑1,3,5‑triaza‑7‑phosphaadamantane). In particular, we have studied the stability of the [Cu(PTA)_n]⁺ species (n = 2-4) in aqueous medium, and their speciation as a function of the total [Cu(PTA)₄]BF₄ concentration by means of competitive UV-visible spectrophotometric titrations using metallochromic indicators. Also, the structure in solution of the Cu(I)/PTA species and the nature of the first coordination sphere of the metal were studied by transformed XAS. Both techniques allowed to study samples with total [Cu(PTA)₄]BF₄ concentration down to 68-74 μM, possibly relevant for biological applications. Overall, our data suggest that the [Cu(PTA)_n]⁺ species are stable in solution, among which [Cu(PTA)₂]⁺ has a remarkable thermodynamic stability. The tendency of this last complex to form adducts with N-donor ligands is demonstrated by the spectrophotometric data. The biological relevance of PTA towards Cu(I), especially in terms of chemotreatments and chelation therapy, is discussed on the basis of the speciation model the Cu(I)/PTA system.

Studying Media Polarity Effects on the Photo-Physical Behaviors of Organometallic Complexes with Azo-Containing Schiff-Base Ligands

Solvent molecules as an important factor can modify the photo-physical behavior of organometallic complexes. For precise investigation, in this paper, the spectral behavior of some groups of copper complexes with different substituents were studied in various solvent media. In this case, the linear solvation energy relationships concept was used for determination of various contribution of media induced specific and non-specific interactions on the photo-physical behavior of various forms of organometallic complexes with azo-containing Schiff-base dyes. Moreover, the calculated dipole moments indicate that samples with different forms tend to have polar structure in the excited state as compared to those in the ground state. By exploiting of calculated dipole moments and obtained quantitative results in the ground and excited states, the dominant solvent induced resonance structures were also estimated. The obtained experimental results can give more information about how these samples can behave in various physical, chemical and biological phenomena.

Cu(i) and Ag(i) complex formation with the hydrophilic phosphine 1,3,5-triaza-7-phosphadamantane in different ionic media. How to estimate the effect of a complexing medium

The complexes of Cu(i) and Ag(i) with 1,3,5-triaza-7-phosphadamantane (PTA) are currently studied for their potential clinical use as anticancer agents, given the cytotoxicity they exhibited in vitro towards a panel of several human tumor cell lines. These metallodrugs are prepared in the form of [M(PTA)₄]⁺ (M = Cu⁺, Ag⁺) compounds and dissolved in physiological solution for their administration. However, the nature of the species involved in the cytotoxic activity of the compounds is often unknown. In the present work, the thermodynamics of formation of the complexes of Cu(i) and Ag(i) with PTA in aqueous solution is investigated by means of potentiometric, spectrophotometric and microcalorimetric methods. The results show that both metal(i) ions form up to four successive complexes with PTA. The formation of Ag(i) complexes is studied at 298.15 K in 0.1 M NaNO₃ whereas the formation of the Cu(i) one is studied in 1 M NaCl, where Cu(i) is stabilized by the formation of three successive chloro-complexes. Therefore, for this latter system, conditional stability constants and thermodynamic data are obtained. To estimate the affinity of Cu(i) for PTA in the absence of chloride, Density Functional Theory (DFT) calculations have been done to obtain the stoichiometry and the relative stability of the possible Cu/PTA/Cl species. Results indicate that one chloride ion is involved in the formation of the first two complexes of Cu(i) ([CuCl(PTA)] and [CuCl(PTA)₂]) whereas it is absent in the successive ones ([Cu(PTA)₃]⁺ and [Cu(PTA)₄]⁺). The combination of DFT results and thermodynamic experimental data has been used to estimate the stability constants of the four [Cu(PTA)_n]⁺ (n = 1-4) complexes in an ideal non-complexing medium. The calculated stability constants are higher than the corresponding conditional values and show that PTA prefers Cu(i) to the Ag(i) ion. The approach used here to estimate the hidden role of chloride on the conditional stability constants of Cu(i) complexes may be applied to any Cu(i)/ligand system, provided that the stoichiometry of the species in NaCl solution is known. The speciation for the two systems shows that the [M(PTA)₄]⁺ (M = Cu⁺, Ag⁺) complexes present in the metallodrugs are dissociated into lower stoichiometry species when diluted to the micromolar concentration range, typical of the in vitro biological testing. Accordingly, [Cu(PTA)₂]⁺, [Cu(PTA)₃]⁺ and [Ag(PTA)₂]⁺ are predicted to be the species actually involved in the cytotoxic activity of these compounds.

Therapeutic potential of the phosphino Cu(I) complex (HydroCuP) in the treatment of solid tumors

[Cu(thp)₄][PF₆] (HydroCuP) is a phosphino copper(I) complex highly soluble and stable in physiological media that has been developed as a possible viable alternative to platinum-based drugs for anticancer therapy. HydroCuP potently inhibited the growth of human cancer cells derived from solid tumors by inducing endoplasmatic reticulum (ER) stress thus leading to cell death through paraptosis with a preferential efficacy against cancer rather than non-cancer cells. Aim of the present study was to assess the therapeutic potential of HydroCuP in vivo, in syngenic and xenograft murine models of solid tumors by triggering the Unfolded Protein Response (UPR) pathway. With respect to platinum drugs, HydroCuP induced a markedly higher reduction of tumor growth associated with minimal animal toxicity. In human colorectal cancer xenografts, chemotherapy with HydroCuP was extremely effective in both oxaliplatin-sensitive and resistant models. The favorable in vivo tolerability of HydroCuP was also correlated to an encouraging biodistribution profile. Additionally, no signs of drug-related neurotoxicity and nephrotoxicity were observed. Altogether, these results demonstrate that HydroCuP appears worth of further investigation to evaluate its therapeutic activity towards a broad spectrum of solid malignancies.

Heteroleptic Copper(I) Complexes of "Scorpionate" Bis-pyrazolyl Carboxylate Ligand with Auxiliary Phosphine as Potential Anticancer Agents: An Insight into Cytotoxic Mode

New copper(I) complexes [CuCl(PPh₃)(L)] (1: L = L_A = 4-carboxyphenyl)bis(3,5-dimethylpyrazolyl)methane; (2: L = L_B = 3-carboxyphenyl)bis(3,5-dimethylpyrazolyl)methane) were prepared and characterised by elemental analysis and various spectroscopic techniques such as FT-IR, NMR, UV–Vis, and ESI-MS. The molecular structures of complexes 1 and 2 were analyzed by theoretical B3LYP/DFT method. Furthermore, in vitro DNA binding studies were carried out to check the ability of complexes 1 and 2 to interact with native calf thymus DNA (CT-DNA) using absorption titration, fluorescence quenching and circular dichroism, which is indicative of more avid binding of the complex 1. Moreover, DNA mobility assay was also conducted to study the concentration-dependent cleavage pattern of pBR322 DNA by complex 1, and the role of ROS species to have a mechanistic insight on the cleavage pattern, which ascertained substantial roles by both hydrolytic and oxidative pathways. Additionally, we analyzed the potential of the interaction of complex 1 with DNA and enzyme (Topo I and II) with the aid of molecular modeling. Furthermore, cytotoxic activity of complex 1 was tested against HepG2 cancer cell lines. Thus, the potential of the complex 1 is promising though further in vivo investigations may be required before subjecting it to clinical trials.

Interaction products of cytotoxic Cu(I) complexes with different solvent mixtures: an electrospray ionization mass spectrometry and density functional theory study

RATIONALE

[Cu(P)₄ ][BF₄ ]-type complexes (P = tertiary phosphine) have shown significant antitumor activity. This biological property appears to be activated via formation of coordinative unsaturated [Cu(P)_n ]⁺ species (n < 4), that may interact with various molecules starting from the solvent(s) in which they are dissolved. Aim of our study was to investigate the interaction of these species with different solvent mixtures.

METHODS

The interaction has been investigated by electrospray ionization mass spectrometry, and the interaction products have been characterized by multiple collisional experiments, using an ion trap mass instrument. Density functional theory (DFT) calculation studies, using a meta-hybrid exchange correlation (xc) functional and an implicit solvent model, were employed to investigate the equilibrium distribution of species in solution.

RESULTS

Depending on the nature of the solvent mixture and coordinated phosphine, three [Cu(P)₄ ][BF₄ ]-type complexes undergo dissociation with formation of [Cu(P)₂ ]⁺ , [Cu(P)(solv)]⁺ and [Cu(solv)₂ ]⁺ species (solv = solvent). Preferred collisional-induced fragmentation pathways provide qualitative information on the selectivity of [Cu(P)_n ]⁺ for specific solvents and donor atoms. Formation free energies and equilibrium constants pertaining to [Cu^I (PTA)_n ]⁺ , [Cu^I/II (solv)_n ]^m+ (n ≤ 4; m = 1, 2) and [Cu^I (PTA)_2-k (sol)_k ]⁺ (k = 1, 2) provide a comprehensive picture of equilibria in solution.

CONCLUSIONS

Dimethyl sulfoxide (DMSO) and acetonitrile (MeCN) strongly affect [Cu(P)_n ]⁺ assemblies producing mixed-ligand [Cu(P)(DMSO)]⁺ and [Cu(P)(MeCN)]⁺ species. Excess of both DMSO and MeCN solvents are able to fully displace coordinated phosphines giving [Cu(solv)₂ ]⁺ -type adducts. The presence of phosphines in the native complex is mandatory to retain the reduced oxidation state of copper. Instead, the more labile [Cu^I (MeCN)₄ ]⁺ complex dissolved in DMSO and MeCN displays a combination of Cu(I) and Cu(II) adducts. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis and C–H activation reactions of cyclometalated copper(i) complexes with NCN pincer and 1,3,5-triaza-7-phosphaadamantane derivatives: in vitro antimicrobial and cytotoxic activity

A series of novel cyclometalated copper(i) complexes with NCN pincer and N-aryl-1,3,5-triaza-7-phosphaadamantane ligands have been synthesized by C–H activation and studied for in vitro antimicrobial and cytotoxic activity.