18432-95-6

Herein the effects of three platinum complexes, namely (SP-4-2)-(2,2′-bipyridine)dichlorido platinum(II), Pt-bpy, (SP-4-2)-dichlorido(1,10-phenanthroline) platinum(II), Pt-phen, and (SP-4-2)-chlorido(2,2′:6′,2′ ′-terpyridine)platinum(II) chloride, Pt-terpy, on the aggregation of an amyloid model system derived from the C-terminal domain of Aβ peptide (Aβ21–40) were investigated. Thioflavin T (ThT) binding assays revealed the ability of Pt(II) compounds to repress amyloid aggregation in a dose-dependent way, whereas the ability of Aβ21–40 peptide to interfere with ligand field of metal complexes was analyzed through UV-Vis absorption spectroscopy and electrospray ionization mass spectrometry. Spectroscopic data provided micromolar EC50 values and allowed to assess that the observed inhibition of amyloid aggregation is due to the formation of adducts between Aβ21–40 peptide and complexes upon the release of labile ligands as chloride and that they can explore different modes of coordination toward Aβ21–40 with respect to the entire Aβ1–40 polypeptide. In addition, conformational studies through circular dichroism (CD) spectroscopy suggested that Pt-terpy induces soluble β-structures of monomeric Aβ21–40, thus limiting self-recognition. Noticeably, Pt-terpy demonstrated the ability to reduce the cytotoxicity of amyloid peptide in human SH-SY5Y neuroblastoma cells. Presented data corroborate the hypothesis to enlarge the application field of already known metal-based agents to neurodegenerative diseases, as potential neurodrugs.

Despite the concerted efforts to develop targeted cancer treatments, these therapies are plagued by the rapid development of resistance and serious adverse drug reactions. Based on the wide clinical use and successes of the platinum drugs like cisplatin and oxaliplatin, we investigated the synthesis and potential anticancer efficacy of alternative platinum complexes. A series of nine cationic square planar platinum(ii) complexes were synthesized and characterized and then evaluated for their anticancer activity. The complexes were of the type [Pt(diimine)(Ln-κO,S)]+where diimine is either 1,10-phenanthroline (phen), 5,6-dimethyl-1,10-phenanthroline (dmp) or dipyrido[3,2-f:2′,3′-h]quinoxaline (dpq) and Ln-κO,Srepresenting variousN,N-dibutyl-N′-acylthiourea ligands. The anticancer activity of the synthesised complexes was evaluated against two lung cancer cell lines (A549 and H1975) and a colorectal cancer cell line, HT-29. The 50% inhibitory concentrations (IC50) for the most cytotoxic compounds were determined and the mode of cell death evaluated. The structure-activity relationships indicated that complexes with the 5,6-dimethyl-1,10-phenanthroline variation of the diimine ligand were the most active against the cell lines tested, while the activity of complexes based on the acylthiourea ligand varied between the cell lines. IC50values for the three active platinum complexes were in the low micromolar range for the three cell lines and ranged between 0.68 μM and 2.28 μM. Changes to cell morphology indicate that the active platinum complexes induce cell death by both apoptosis and paraptosis. The complexes were able to induce the nuclear expression of the cyclin-dependent kinase inhibitor, p21, which is an indicator of DNA damage. The collective data indicate that these platinum complexes are valuable lead compounds for further analysis and cancer drug discovery.

The focus of this work is pointing out the different behavior of two structurally related Pt(II) complexes, the anionic cyclometalated NBu4[(Bzq)Pt(Thio)], 1 and the neutral [(Phen)Pt(Thio)], 2, (Bzq = benzo[h]quinoline, Phen = 1,10-phenantroline, Thio = 1,2-benzenedithiolate), on the interaction with human serum albumin (HSA), a key drug-delivery protein in the bloodstream. Being very limited the number of anionic Pt(II) complexes reported to date, this is a pioneering example of report on a protein-ligand interaction involving a negatively charged platinum compound. The study was carried out by using fluorescence spectroscopy, differential scanning calorimetry and molecular docking simulations. The results revealed a strong binding affinity between the anionic compound and the protein, whereas a weak/moderate binding interaction was highlighted for the neutral one. Comparative studies with site specific ligands (warfarin and ibuprofen), allowed us to identify the protein binding sites of the two compounds. The work aims to shed light on the relevance of the charge in designing new drugs with a favorable binding affinity for HSA, which strongly contributes to influence their pharmacological and toxicological profile.

Four platinum complexes, formulated as [Pt(phen)(OCOCH2OR)2] (phen=1,10-phenanthroline, R=Me, Et, iPr, or tBu), have been synthesized and well characterized by elemental analysis, IR, 1H-NMR, 13C-NMR and ESI-MS spectroscopy. Replacing chloride groups of the precursor Pt(phen)Cl2 with alkoxyacetate anions greatly improved the aqueous solubility and cytotoxicity of the resulting platinum complexes. The in vitro cytotoxicity study revealed that complexes 1–3 were active in vitro towards four human tumor cell lines, especially complex 1 which exhibited prominent in vitro cytotoxic activity against HCT-116 cell lines comparable to cisplatin and oxaliplatin. Flow cytometry assay indicated that representative complexes 1 and 2 exerted cytotoxicity on HCT-116 cell lines through inducing cell apoptosis and blocking cell cycle progression in the S or G2/M phases. The interaction of representative complexes with pET28a plasmid DNA was tested by agarose gel electrophoresis, which demonstrated that complexes 1 and 2 were capable of distorting plasmid DNA mainly by covalent binding and degradation effect.

The mixed-ligand [Pt(phen)(L1-κS)2] complex, in which two N,N-diethyl-N′-1-naphthoylthioureato ligands (L1)- coordinate in an unusual κS-thio/amido mode, crystallises in two solvatomorphs, form I and form II, whose structures have been determined by single crystal X-ray diffraction. These crystals were obtained from tetrahydrofuran and methanol/water respectively showing interesting sandwich (form I) and half-sandwich (form II) intramolecular π-stacking arrangements between the naphthoyl moiety of the acylthioureato ligands and the 1,10-phenanthroline ligand that adopt an anti-conformation above and below the square planar coordination plane. Variable temperature 1H and 195Pt NMR spectroscopy showed that these π-stacking arrangements persist in methanol solution especially at lower temperatures, where significant chemical shift shielding and asymmetry are observed indicating at least 3 conformers at -50 °C. A preliminary study indicates that this new compound may have potential as a new anticancer agent since it is active against the A549 lung cancer cell-line with an IC50 value of 6 ± 0.9 μM.

Mixed-ligand platinum(ii) complexes, [Pt(phen)(pacac)](NO3) (1), [Pt(phen)(cur)](NO3) (2), [Pt(bt-phen)(cur)](NO3) (3) and [Pt(phen)(scur)](NO3) (4), where phen is 1,10-phenanthroline, bt-phen is 5-biotin-1,10-p

The series of complexes of formula [PtCl(η2-olefin)(N^N)]+, previously investigated for N^N = N,N,N′,N′-tetramethyl-ethylenediamine (Me4en), has been extended to the case of aromatic diimines 1,10-phenanthroline (phen) and 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4phen) and to a variety of olefins (ethene, propene and styrene). The complexes have been prepared by reaction of the [PtCl3(η2-olefin)]? anions (K[PtCl3(η2-styrene)] reported here for the first time) with N^N in basic methanol. The initial [PtCl{η1-CH2–CH(R′)–OMe}(N^N)] (R′ = Me, Ph) complexes are formed in quantitative yield and as pure Markovnikov isomer. The reaction of the alkoxylic species with non coordinating acids, results in the quantitative formation of the desired cationic π-olefin complexes [PtCl(η2-olefin)(N^N)]+. The phenanthroline ligand confers peculiar properties to the new compounds. In particular, by reaction with triethylamine, [PtCl{η2-CH2[dbnd]CH(Me)}(N^N)]+ species, undergo deprotonation of the olefin and formation of the dimeric species [{PtCl(N^N)}2(μ-η1:η2-CH2CH[dbnd]CH2)]+ which could be isolated and characterized. Interestingly such product in acetonitrile gives a disproportionation with precipitation of [PtCl2(phen)] and formation in solution of the new η3-allyl complex [Pt(η3-C3H5)(phen)]ClO4.

Four platinum(IV) complexes containing intercalating ligands [1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy)] and ancillary ligands [(1S,2S)-diaminocyclohexane (SS-DACH) and (1R,2R)-diaminocyclohexane (RR-DACH)] were synthesized and characterized by 1H nuclear magnetic resonance, electrospray ionization mass spectrometry, X-ray crystal structure analysis, elemental analysis, ultraviolet absorption spectroscopy, circular dichroism spectroscopy, and electrochemical analysis. The reactions between [Pt(phen)(SS-DACH)Cl2]2+ and glutathione and Ac-CPFC-NH2 were investigated by high-performance liquid chromatography. [Pt(phen)(SS-DACH)Cl2]2+ was reduced to its corresponding Pt(II) complex [Pt(phen)(SS-DACH)]2+, while glutathione and Ac-CPFC-NH2 were oxidized to glutathione-disulfide and a peptide containing an intramolecular disulfide bond, respectively. The cytotoxicities of the Pt(IV) complexes against a human non-small cell lung cancer cell line (A549) and the corresponding cisplatin-resistant cell line (A549cisR) were evaluated. These Pt(IV) complexes showed a higher activity toward A549 and A549cisR than did cisplatin. Also, the cytotoxicities of the Pt(IV) complexes were higher for A549cisR than for A549 cells. Moreover, the cytotoxicities of the (SS-DACH)-liganded platinum complexes were higher than those of the (RR-DACH)-liganded platinum complexes in either A549 or A549cisR cells. Phen-liganded platinum complexes were more cytotoxic than the bpy-liganded platinum complexes. The cytotoxicities of these Pt(IV) complexes had no correlation with reduction potentials.

The present study highlights the importance of understanding the structural changes of micelles induced by drug loading on their physico-chemical properties. A block copolymer with attached fructose, which interacts with GLUT5 receptor, was used and conjugated with a low and a high amount of platinum drugs. Against expectations, the low-loading micelle, despite having a less defined morphology and larger nanoparticle size according to TEM, displays higher cellular uptake and higher toxicity. This behaviour can only be understood when elucidating additional information on the structure of micelles. Extensive solid-state NMR measurements were therefore employed to reveal that the drug loading affected swelling and mobility of core and shell of the micelle. The results obtained from solid-state NMR spectroscopy could explain all the observations on this system. In summary, solid-state NMR spectroscopy is an excellent tool to understand the effects of drug loading on the behavior of micelles.

Reaction between [Pt(ophen)Cl2] and HIS was monitored and the solvolysis (k1) and Cl/HIS ligand exchange (k2) rate constants obtained. The k1 and k2 were (6.2?±?0.4)?×?10?5?s?1 and 52.8?×?10?2?M?1?s?1, respectively. The corresponding calculated values were 47.5?×?10?5?s?1 and 52.2?×?10?2?M?1?s?1, in agreement with the experiment. Calculations were used to establish the reactivity order for a set of amino acids: MET?～?LYS?～?HIS(ε)?>?GLU?～?ASP?>>?ASN?～?GLN. In spite of the similar reactivity among MET, LYS and HIS, the thermodynamics suggests the reactions with LYS and HIS more favorable than with MET. Therefore, N-containing amino acids should be potential targets of Pt(II)-complexes in β-amyloid.

The aim of this study was to investigate the structure effect and identify the modes of binding of amino acid-Pt complexes to DNA molecule for cancer treatment. Hence, three novel water soluble platinum complexes, [Pt(phen)(R-gly)]NO3 (where phen is 1,10-phenanthroline, R-gly is methyl, amyl, and isopentyl-glycine), have been synthesized and characterized by spectroscopic methods, conductivity measurements, and chemical analysis. The anticancer activities of synthesized complexes were investigated against human breast cancer cell line of MDA-MB 231. The 50% cytotoxic concentration values were determined to be 42.5, 58, and 70 μm for methyl-, amyl-, and isopentyl-gly complexes, respectively. These complexes were interacted with calf thymus DNA (ct-DNA) via positive cooperative interaction. The modes of binding of the complexes to DNA were investigated by fluorescence spectroscopy and circular dichroism in combination with a molecular docking study. The result indicates that complexes with small or branched hydrocarbon chains can intercalate with DNA. This is while amyl complexes with linear chains interacted additionally via groove binding. The results of the negative value of Gibbs energy for binding of isopentyl-platinum to DNA and those of the molecular docking were coherent. Furthermore, the docking results demonstrated that hydrophobic interaction plays an important role in the complex–DNA interaction.

PROBLEM TO BE SOLVED: To provide a platinum complex more excellent in anticancer activity than the coexisting platinum anticancer such as cisplatin and oxaliplatin, and also reduced in side-effects. SOLUTION: Provided is a platinum complex represented by formula (1) as a myo-inositol-1,2,3,4,5,6-hexakisphosphate derivative, and also provided is a platinum complex such as a (1,10-phenanthroline)(N-9-anthranilic methyl-1, 4-butane diamine) platinum [m and n respectively independently denote 1 or 2 and m+n denotes 3]. SELECTED DRAWING: None COPYRIGHT: (C)2016,JPOandINPIT

Five new [Pt(N∧N)(dtoc)] complexes (1-5; N^N = diimine: 2,2′-bipyridine and its 4,4′-alkyl/aryl-substituted derivatives or 1,10-phenanthroline; dtoc2- = 1,2-dithiolate-1,2-closo- dicarbadodecaborane) have been synthesized and characterized by spectroscopic and electrochemical methods, and by means of X-ray diffraction in the case of complexes 1 and 4. Hybrid DFT and time-dependent (TD) DFT calculations were performed on complexes 1-5 and the previously reported complex [Pt(Ph 2phen)(dtoc)] (6; Ph2phen = 4,7-diphenyl-1,10- phenanthroline) both in the gas phase and in the presence of several solvents (CH2Cl2, CHCl3, CH3CN, acetone, THF, DMF, DMSO, and toluene) to gain an insight into the electronic structure of the complexes and explain their experimental features. Theoretical calculations allowed for the determination of structure-property relationships within the series of the six complexes considered, and the prediction of their second order nonlinear optical (SONLO) properties by evaluating their first static hyperpolarizabilities (βtot). the Partner Organisations 2014.

We have recently reported the synthesis, characterisation and dynamic behaviour of 10 [Pd(bipy)(R-TU)2]Cl2 and [Pd(phen)(R-TU)2]Cl2 (bipy = 2,2′-bipyridyl; phen = 1,10-phenanthroline; R-TU = N-alkyl substituted thioureas) complexes; in this paper PtII analogues are presented to achieve a complete overview on this class of molecules. As expected, PtII derivatives increase the rotation barrier about the thioureas C-N bonds and once again the metal has proved to select preferential conformations for both mono and dialkyl thioureas. In this study, beyond the many shared features of the 20 PtII and PdII complexes, we extensively issue all the data concerning 13C, 15N and 195Pt hetero-nuclear NMR, stressing out the chemical shift differences that any free ligand undergoes upon coordination. To achieve this goal all the hetero-nuclear experiments were performed for the 7 free ligands and the 20 complexes in the same experimental conditions. Further support to the determined structures and dynamics is provided by mass spectrometry measurements by an ion-trap time-of-flight (IT-TOF) detector.

The reactions of water with the coordinatively unsaturated group 10 organometallic cations [(L)M(R)]+ (4; where L = 1,10-phenanthroline (phen), neocuproine (neo); M = nickel, palladium, platinum; R = CH3, C6H5, CH2C6H5), formed via decarboxylation of the carboxylate complexes [(L)M(O2CR)] +, were examined in the gas phase using a combination of multistage mass spectrometry experiments and DFT calculations at the M06/SDD6-31+G(d) level of theory. Two main types of primary product ions were observed: the aqua adduct [(L)M(R)(H2O)]+ (5) and the hydroxide [(L)M(OH)]+ (7), formed via a hydrolysis reaction. A secondary product ion, arising from formation of the adduct [(L)M(OH)(H 2O)]+, was also observed when L = phen, R = CH 3, and M = Pt. The rates of reaction of 4 and the product branching ratios for 5 and 7 were dependent upon the nature of M, L, and R. When L = phen and R = CH3, the hydroxide 7 dominates for Ni, with the adduct 5 as the major product for both Pd and Pt. For R = C6H5 the rate of the reaction is slower, while for R = CH2C6H 5 no reaction occurs. Replacing the phen auxiliary ligand with neo dramatically slows down the rate of reaction with water. DFT calculations reveal that an acid-base hydrolysis mechanism is favored over an oxidative addition/reductive elimination mechanism proceeding via the M(IV) intermediate [(L)M(CH3)(H)(OH)]+. Furthermore, the relative energies calculated for the barriers of these hydrolysis reactions are consistent with the experimentally observed reactivity trends. This mechanism is also supported by RRKM theory/master equation simulations, which demonstrate that formation of the aqua adduct and hydroxide can be explained by competition between unimolecular dissociation and collisional deactivation of the chemically activated reaction adduct within the ion trap. The lack of reactivity of the benzyl systems appears to arise from η3 binding of the benzyl group, which blocks access to the incoming water. Finally, links are made to group 10 three-coordinate organometallic complexes in the condensed phase.

The binding site specificity of the ternary complexes, [M(ii)(phen)(edda)] (M(ii) = Pt2+ and Zn2+; phen = 1,10-phenanthroline; edda = N,N′-ethylenediaminediacetic acid), for the self-complementary oligonucleotides (ODNs), ds(C1G2C3G 4A5A6T7T8C 9G10C11G12)2 (ODN1) and ds(C1G2C3G4T5A 6T7A8C9G10C 11G12)2 (ODN2), was studied by NMR measurements. The results indicated that [Pt(ii)(phen)(edda)] was partially intercalated between C3/G10 and G4/C 9 base pairs of ODN1 and ODN2 in the major grooves, whereas [Zn(ii)(phen)(edda)] was bound specifically to the TATA region of ODN2 in the minor groove and to the terminal G2/C11 base pair of ODN1 in the major groove. The preference for the TATA sequence over the AATT sequence in the binding of [Zn(phen)(edda)] was attributed to the wider minor groove width of the TATA sequence. The bindings of the complexes to ct-DNA were also studied by UV, CD, and fluorescence spectroscopy. Additionally, the antiproliferative property of [Pt(ii)(phen)(edda)] towards MCF7 breast cancer cells and normal MCF10-A cells was compared with that of [Zn(ii)(phen)(edda)].

A yet unreported polymorph of [PtCl2(1,10-phenanthroline)] was obtained by slow decomposition, in CH2Cl2 solution, of [Pt{CH2CH2N(CH2CH3) 2-κC,κN}(1,10-phenanthroline)](ClO4). The structure of the new orthorhombic form, III, (space group Pna21), is described and compared to those of the two already reported forms, I and II, which are monoclinic (space group P21/c) and orthorhombic (space group Pca21), respectively [21]. Polymorph III appears to be the least stable of the three.

A series of new N2S2 mixed ligand transition metal complexes, where N2 is phenanthroline and S2 is 1,2-dithiooxalate (dto) or 1,2-dithiosquarate (dtsq), has been synthesized and characterized. IR spectra reveal that the 1,2-dithiolate ligands are coordinated via the sulfur atoms forming a N2S2 coordination sphere. The copper(II) complex [Cu(phen)(dto)] was studied by EPR spectroscopy as a diamagnetically diluted powder. The diamagnetic dilution resulted from doping of the copper complex into the isostructural host lattice of the nickel complex [Ni(phen)(dto)]. The electronic situation in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of EHT and DFT calculations. Furthermore, one side product, chlorobis(1,10-phenanthroline)copper(I) ethanol solvate hydrate [(phen)2CuCl]·C2H5OH·H2O, was formed by a reduction process and characterized by X-ray diffraction. In the crystal packing one-dimensional columns of dimers are formed, stabilized by significant π-π interactions.

Competing outer-sphere self-association of [PtII(1,10-phen- anthroline)(N-pyrrolidyl-N-(2,2-dimethylpropanoyl)thiourea)]+ Cl(M) and the hetero-association of M with fluoranthene (F) have been investigated by means of the significant concentration dependence of 1H NMR chemical shifts as well as by diffusion coefficients obtained from DOSY NMR spectroscopy. The NMR spectroscopic data is only consistent with the formation of a "dimer" M-M aggregate according to 2MM2 in acetonitrile at several temperatures, with a calculated KD of ca. 46 ± 7 M-1 at 273.5 K. In the presence of the aromatic molecule fluoranthene, relatively strong, presumably π-cation-type interactions between M and F according to M + FMF (KB≈67 ± 7 M -1 at 273.5 K) occur in acetonitrile. The calculated ΔrH° and ΔrS° for M-M (-25129 ±3112 and -61 ± 11 Jmol-1) and M...F (-13560±3180 and -17 ±11 J mol-1, respectively) is indicative of π-cation interactions. Interestingly any potential F-F aggregation interactions are negligible for the fluoranthene concentration range up to 0.1 M, indicating that non-covalent π-π interactions between fluoranthene molecules 2FF2 are, in contrast to πcation interactions, negligible under these conditions in solution. Wiley-VCH Verlag GmbH and Co. KGaA, 69451 Weinheim, Germany, 2009).

PtII azido complexes [Pt(bpy)(N3)2] (1), [Pt(phen)(N3)2] (2) and trans-[Pt(N3) 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 (N3-Pt-N3 angle 146.7°) as a result of steric congestion at the Pt centre. The novel Pt IV complexes trans, cis-[Pt(bpy)(OAc)2(N3) 2] (4), trans, cis-[Pt(phen)(OAc)2(N3) 2] (5), trans, trans, trans-[Pt(OAc)2(N3) 2(py)2] (6), were obtained from 1-3via oxidation with H2O2 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 PtIV complexes exhibit greater absorption at longer wavelengths (ε = 9756 M-1 cm-1 at 315 nm for 4; ε = 796 M-1 cm-1 at 352 nm for 5; ε = 16900 M-1 cm-1 at 307 nm for 6, in aqueous solution) than previously reported PtIV 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 PtIV electronic and structural properties allowed further elucidation of the photochemistry of 4-6. The Royal Society of Chemistry 2009.

The reactions between allyl compounds CH2CHCH2Fn bearing electron-withdrawing functional (Fn) groups and cationic {Pt(aryl)(1,10-phenanthroline)}+ fragments generated in situ are described. The aryl and platinum addition to the terminal and, respectively, internal unsaturated carbon is generally observed. The subsequent H-C aryl bond activation, followed by HFn elimination, affords the ortho organic fragment (Pt)-aryl-CH2CHCH2 η1, η2-chelate to the platinum. This process does not occur when the regiochemistry is of Markownikov type and the Pt-CH2CH(aryl)CH 2Fn fragment is formed. The described results are compared with those concerning the behaviour of unsubstituted α-olefins. The X-ray crystal structure of the title five-coordinate complex shows a distorted tbp arrangement of the ligands with the iodide in the equatorial plane and the unusual axial-equatorial coordination mode of the 1,10-phenanthroline.

The steric hindrance generated by carrier ligands, in particular in cis-PtA2G2 adducts (A2 = diamine, (G = guanine derivative), has often been used to slow down rotation about the platinum-guanine bonds, thus allowing the characterisation of different conformers and the analysis of the interactions that are involved in the stabilisation of cisplatin adducts with DNA. In a previous study concerning 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline (phen and Me2phen, respectively), the Me2phen ligand was reported to form an unusual bis-guanosine derivative with a trans disposition of the nucleobases and monodentate Me2phen. The present investigation has demonstrated that phen and Me2phen, like other bidentate ligands, allow formation of both mono- and bis-guanosine derivatives, the latter having the usual cis configuration. In both the phen and Me2phen carrier ligands the rigidity of the phenanthroline skeleton is able to hinder rotation of the guanosine base(s) about the Pt-N(7) bond(s) and render the interconversion between rotamers slow on the NMR timescale even at 350 K (the highest temperature explored). However there are noticeable differences between the two ligands. As a consequence of the increased in-plane steric bulk of Me2phen: (i) the H(8) chemical shifts within the HH (Head-to-Head) conformer and between the HT (Head-to-Tail) conformers become closer, (ii) the average H(8) chemical shift of the HT conformers is at higher field and that of the HH form at lower field, and (iii) the HT rotamers become even more favoured than the HH rotamer. Observation (ii) is in agreement with the HT rotamers preferring the 6- in conformation, which brings the six-membered rings of the guanines closer to one another and is also in agreement with the phen ligand allowing a greater canting of the guanine bases than Me2phen. Moreover, free chloride ion readily displaces the coordinated guanosines, particularly in solvents of lower dielectric constants than water. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Two salts of (ethylenediamine-N,N′)(1,10-phenanthroline-N, N′)platinum(II), namely the dichloride dihydrate, [Pt(C2H8N2)(C12H8N 2)]Cl2·H2O, (I), and the bis(hexafluorophosphate), [Pt(C2H8N2)(C12H8N 2)](PF6)2, (II), have π-phenanthroline-stacked structures. The interplanar spacings of the π-π stacks, however, are quite different in the two salts, being 3.38 (1) and 3.40 (1) A for (I), and 3.60 (5) and 3.56 (5) A for (II). These are controlled by the anions located on the aliphatic sites.

The reactions of [Ni(aet)2] with [PtCl2(L)] gave a new type of S-bridged dinuclear complexes [Pt(L){Ni-(aet)2(H2O)2}]2+ (aet=aminoethanethiolate; L=bpy=2,2′-bipyridine, phen=1,10-phenanthroline (5), dmbpy=4,4′-dimethyl-2,2′-bipyridine). These complexes readily react with L′ to form [M(L){Ni(aet)2(L′)}]2+ (L=bpy, L′=bpy (3), phen; L=phen, L′=phen, bpy; L=L′=dmbpy). A similar reaction of [Ni(aet)2] with [PtCl2(phen)] and phen gave only [Pt-(phen){Ni(aet)2(phen)}]2+. The crystal structures of 3 and 5 were determined by X-ray crystallography. The Ni atoms are surrounded by two aet and a bpy or two water molecules to have an approximately octahedral geometry, forming the C2-c/s(S)-[Ni(aet)2{bpy or (H2O)2}] unit. The Pt atoms have a square-planar geometry, in which two Cl atoms of the starting [PtCl2(L)] (L=bpy or phen) have been substituted by the two S atoms from the Ni(II) unit. The Pt(II) plane and the Ni(II) equatorial plane are almost coplanar, and the Pt-Ni distance is 3.4987(8) A (3) and 3.476(4) A (5). All of the complexes were characterized on the basis of the electronic absorption and infrared spectra and the cyclic voltammetry. The conversion of a square-planar [Ni(aet)2] to an octahedral [Ni(aet)2{(H2O)2 or (L′)}] units was also considered. In the solid state, the water molecule in [Pt(L){Ni(aet)2(H2O)2}]2+ could be readily exchanged by nitrate.

Photochemical and photophysical properties of eight square-planar Pt(II) dithiolate diimine complexes (4-XC6H4S)2(NN)Pt (where (NN) is 1,10-phenanthroline or 2,2'-bipydine; X = NO2, H, OMe, Me2N) were

Two series of Pt(diimine)(dithiolate) complexes have been prepared in order to investigate the effects of molecular design on the excited-state properties of this chromophore. The first series comprises Pt(dbbpy)(dithiolate) complexes where dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine and the dithiolates are 1-(tert-butylcarboxy)-1-cyanoethylene-2,2-dithiolate (tbcda), 1-diethylphosphonate-1-cyanoethylene-2,2-dithiolate (cpdt), 6,7-dimethylquinoxaline-2,3-dithiolate (dmqdt), maleonitriledithiolate (mnt), and toluene-3,4-dithiolate (tdt). The second series comprises Pt(diimine)(tdt) complexes where the diimines are 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), 4,4'-di-tert-butyl-2,2'-bipyridine (dbbpy), 4,4'-dimethyl-2,2'-bipyridine (dmbpy), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 5-chloro-1,10-phenanthroline (Cl-phen), 4,4'-dichloro-2,2'-bipyridine (Cl2bpy), and 4,4'-bis(ethoxycarbonyl)-2,2'-bipyridine (EC-bpy). All of the compounds display solvatochromic absorption bands and solution luminescence, which are attributed to a common charge-transfer-to-diimine excited state. The excited-state energies can be tuned by approximately 1 eV through ligand variation. Solution lifetimes range from 1 ns to over 1000 ns and Φ(em) range from 6.4 x 10-3 to less than 10-5 in CH2Cl2. Based on these data, the nonradiative and radiative decay rate constants have been calculated. For the Pt(diimine)(tdt) series, the nonradiative decay rate constants increase exponentially with decreasing energy, in agreement with the Energy Gap Law, while those for the Pt(dbbpy)(dithiolate) complexes do not exhibit a similar correlation. Excited-state redox potentials have been estimated for all of the complexes from spectroscopic and electrochemical data. The ability to tune the driving force for bimolecular excited-state electron-transfer reactions has been demonstrated for eight of the complexes using reductive and oxidative quenching experiments.

The effect of the phenanthroline substituents on the structure and reactivity of platinum(II) and platinum(IV) complexes has been investigated. The X-ray crystal structures of the compounds [PtI2(4,7-Ph2phen)]·CHCl3 (1dz·C

The syntheses and characterization, via 1H and 13C NMR spectroscopy and X-ray crystallography, of several new C-malonato Pt(II) and Pt(IV) complexes are described. Cis acyclic bis complexes of C-metalated dimethyl malonate [e.g. Pt(phen)(C5H7O4)2], potential anti-tumor agents, were found to react with X2 and CuX2 (X = Cl, Br) to give the corresponding oxidized products but did not react with acyl halides or methyl vinyl ketone. Two new trans cyclometalated Pt(II) complexes, having 5- and 6-membered C,N-chelates, and a novel cyclometalated bridged acetate dimer were characterized by X-ray crystallography. C22H24N2O8Pt: a = 9.590 (2) ?, b = 29.594 (7) ?, c = 8.442 (2) ?, β = 106.02 (2)°, monoclinic, P21/c, Z = 4. C24H28N2O8Pt: a = 10.0905 (12) ?, b = 23.555 (2) ?, c = 10.823 (3) ?, β = 106.23 (2)°, monoclinic, P21/n, Z = 4. C26H30N2O12Pt2: a = 10.446 (5) ?, b = 16.669 (3) ?, c = 17.038 (3) ?, β = 97.19 (3)°, monoclinic, P21/n, Z = 4.

The synthesis and characterization are described for compounds abbreviated (a) 1-5: [Pd(phen)(OO)], where OO = the dianion from 1,2-ethanediol (1), (+)-1,2-propanediol (2), (±)-2,3-butanediol (3), (-)-1,2-butanediol (4), catechol (5); (b) the sulphur analogue (6) [Pd(phen)(SCH2CH2S)], from ethane-1,2-dithiol; (c) the platinum analogue (7) [Pt(phen)(OCH2CH2O)]; (d) the 2,2′-bipyridyl analogue (8), [Pd(bipy)(OCH2CH2O)] (phen = 1,10-phenanthroline and bipy = 2,2′-bipyridyl).

It is shown that platinacyclobutanes derived from methylcyclopropane exist as a mixture of isomers with partial structures PtCH2CHMeCH2 and PtCH2CH2CHMe, and that these isomers interconvert easily.In some cases decomposition of these platinacyclobutanes gives ylide complexes L>, e.g.L = 2-methylpyridine, while in other cases but-1-ene complexes , e.g.L = CD3CN, are formed.In both cases the products are formed selectively from the least stable isomer of the platinacyclobutane.At higher temperatures or on photolysis, platinacyclobutane complexes such as decompose to give but-1-ene, 2-methylpropene, propene, and ethylene and the relative yields depend on the experimental conditions.Possible mechanisms are discussed.