Reactivity of platinum(II) triphenylphosphino complexes with nitrogen donor divergent ligands

Dinuclear platinum(II) complexes [{PtCl2(PPh3)}2(μ-N–N)], where N–N is a divergent bidentate nitrogen ligand, were prepared by reacting cis-[PtCl2(PPh3)(NCMe)] with N–N in a Pt/N–N molar ratio 2. The (trans,trans)-isomers were obtained as kinetic products and recovered in good yields and high purity {1, N–N = pyrazine (pyrz); 2, N–N = 4,4′-bipyridyl (bipy); 3, N–N = piperazine (pipz); 4, N–N = p-xylylendiamine (xylN2)}. Cis-[PtCl2(PPh3)(NCMe)] was also reacted with the tridentate divergent ligand 2,4,6-tris-(pyrid-4′-yl)1,3,5-triazine (py3TRIA) in molar ratio 3 with formation of the trinuclear (trans,trans,trans)-[{PtCl2(PPh3)}3(μ-py3TRIA)], 5. On the other hand, the treatment of cis-[PtCl2(PPh3)(NCMe)] with the monodentate pyridine (py) produced a mixture of both trans-[PtCl2(PPh3)(py)] (6a) and cis-[PtCl2(PPh3)(py)] (6b). The reactions of cis-[PtCl2(PPh3)(NCMe)] with N–N = pyrz, bipy, pipz, carried out with a Pt/N–N molar ratio 1, were monitored by 31P NMR spectroscopy. Equilibria were observed in solution, involving dinuclear (trans–trans)-[{PtCl2(PPh3)}2(μ-N–N)], mononuclear [PtCl2(PPh3)(N–N)] and free N–N. The addition of an excess of the divergent ligand allowed the complete conversion to the corresponding mononuclear complexes. With the heteroaromatic ligands both geometric isomers were observed (7a, 7b and 8a, 8b, for pyrz and bipy derivatives, respectively) while with pipz the trans-isomer only was detected, 9. In the system involving bipy, the scarcely soluble dinuclear (cis,cis)-[{PtCl2(PPh3)}2(μ-bipy)], 2b, was also obtained. Products 2, 2b, 3·2(CHCl3) and 6a·0.5(C2H4 Cl2) were structurally characterized by single crystal X-ray diffraction methods

Synthesis and reactivity of platinum(II) triphenylphosphino complexes with aromatic aldoximes

trans-[Pt(μ-Cl)Cl(PPh3)]2 reacted with arylaldoximes in 1,2-dichloroethane to afford [PtCl2(PPh3){N(OH)=CHAr}] (Ar = 3,4-dimethoxyphenyl, 1-naphthyl, 9-anthryl) where aldoxime ligands are N-coordinated to platinum. The obtained complexes are soluble in chlorinated solvents, where they afford equilibrium mixtures of cis,trans and/or (E),(Z) isomers. Equilibria in solution were studied by 31P-NMR spectroscopy and solid state structural data were obtained by single crystal X ray diffraction studies. The reactivity of [PtCl2(PPh3){N(OH)=CHAr}] complexes with basic aqueous solutions was studied, under liquid-liquid phase transfer catalysis conditions. The outcome of the reaction depends on the stereochemistry of the precursors: cis,(Z)-isomers promptly undergo cyclization to the corresponding dinuclear derivatives [Pt{μ-(2-N,O)}- {N(O)=CHAr}Cl(PPh3)]2, where two aldoximate ligands symmetrically bridge two metal centers

Synthesis and DNA binding tests of a fluorescent pyrene bearing a Pt(II) pyridineimino complex

Despite the long time gone respect to the discovery of cis-platinum anticancer activity, still a huge amount of research is devoted to the design of new Pt(II) complexes with enhanced biological activity [1-3]. The here presented work concerns the synthesis of a fluorescent pyridinimino platinum(II) complex, where the presence of a cis-platinum moiety linked to an extended aromatic residue could provide interesting properties as for binding to biosubstrates. In fact, covalent Pt(II) binding can occur, which would be strengthened by the anchoring offered by possible intercalation in nucleic acids of the pyrene fragment. Antiproliferative properties have been described for some pyridinimino [4] and pyridinamino [5] platinum(II) complexes. Moreover, similar bifunctional systems have already been tested with interesting performances [7,8]. The chelating iminopyridine ligand was prepared by a condensation reaction between pyridine-2-carboxyaldehyde and the suitably O-alkylated aminoalcohol. The platinum complex was then synthesized starting from cis-[PtCl2(DMSO)2], and purified by crystallization. The pure complex (elemental analysis) was spectroscopically (IR, 1H-, 13C and 195Pt NMR) characterized. It is well soluble in DMSO and in DMSO/H2O mixtures, where its stability was checked by 1H- and 195Pt NMR. The absorbance and fluorescence optical features of the dye were also checked. Afterwards, the target Pt(II) complex was let interact with natural double stranded DNA to check its reactivity towards this biosubstrate. Spectrophotometric and spectrofluorometric titrations show that the binding does indeed occur. As for absorbance data, hypochromic and bathochromic effects suggest intercalative binding. However, the absence of a defined isosbestic point indicates multiple equilibria. Interestingly and in agreement with this observation, the light emission behavior of the dye/DNA system is complex. Opposite fluorescence change trends are observed at different temperatures, likely related to a different contribution of DNA-templated dye aggregation. Under the (until now) explored conditions, the binding is so strong to turn to be quantitative. Further experiments are ongoing to better enlighten the binding mechanism. References: [1] S. X. Chong, S. C. F. Au-Yeung, K. K. W. To, Current Medicinal Chemistry 2016, 23(12), 1268-12. [2] L. Cai, C. Yu, L. Ba, Q. Liu, Y. Qian, B. Yang, C. Gao, Applied Organometallic Chemistry 2018, 32(4). [3] M. Hanif, C. G. Hartinger, Future Medicinal Chemistry 2018, 10(6), 615-617. [4] B. A. Miles, A. E. Patterson, C. M. Vogels, A. Decken, J. C. Waller, P. Jr. Morin, S. A. Westcott, Polyhedron 2016, 108, 23-29. [5] S. Karmakar, K. Purkait, S. Chatterjee, A. Mukherjee, Dalton Trans. 2016, 45, 3599-3615. [6] S. Hochreuther, R. van Eldik, Inorg. Chem., 2012, 51 (5), 3025-3038. [7] C. Bazzicalupi, A. Bencini, A. Bianchi, T. Biver, A. Boggioni, S. Bonacchi, A. Danesi, C. Giorgi, P. Gratteri, A. Marchal Ingraín, F. Secco, C. Sissi, B. Valtancoli, M. Venturini, Chemistry – A European Journal 2008, 14(1), 184-196. [8] S. Biagini, A. Bianchi, T. Biver, A. Boggioni, I.V. Nikolayenko, F. Secco, M. Venturini, Journal of Inorganic Biochemistry 2011, 105, 558-562

A convenient synthesis of highly luminescent lanthanide 1D-zigzag coordination chains based only on 4,4′-bipyridine as connector

The coordination polymers View the MathML source·C7H8 (Ln = Eu, β-dik = dbm, tta, hfac; Ln = Tb; β-dik = dbm; Hdbm = dibenzoylmethane, Htta = thenoyltrifluoroacetone, Hhfac: hexafluoroacetylacetone) were easily assembled in mild conditions and high yields starting from the anhydrous lanthanide β-diketonates as nodes and 4,4′-bipyridine (bpy) as connector. X-ray single crystal studies have shown zigzag extended chains where lanthanide centres are 8-coordinated in a distorted square-antiprismatic geometry. Photoluminescence studies show bright red europium emission and spectral features dependent on the topology of the polymeric chains

New trans dichloro (triphenylphosphine)platinum(II) complexes containing N-(butyl),N-(arylmethyl)amino ligands: Synthesis, cytotoxicity and mechanism of action

Some new platinum(II) complexes have been prepared, of general formula trans-[PtCl2(PPh3)NH(Bu)CH2Ar], where the dimension of the Ar residue in the secondary amines has been varied from small phenyl to large pyrenyl group. The obtained complexes, tested in vitro towards a panel of human tumor cell lines showed an interesting antiproliferative effect on both cisplatin-sensitive and -resistant cells. For the most cytotoxic derivative 2a the investigation on the mechanism of action highlighted the ability to induce apoptosis on resistant cells and interestingly, to inhibit the catalytic activity of topoisomerase II

Partial and exhaustive hydrolysis of lanthanide N,N-dialkylcarbamato complexes. A viable access to lanthanide mixed oxides

Partial hydrolysis (H2O/Ln molar ratio = ¼) of lanthanum di-iso-propylcarbamato complex, [La(O2CNiPr2)3], 1, afforded the tetranuclear μ-oxo derivative [La4O(O2CNiPr2)10], 2, which was structurally characterized by single crystal X-Ray diffraction studies. The carbonatocarbamato derivative of lanthanum, [La4(CO3)(O2CNBu2)10], 3, was prepared by extraction of lanthanum ions from aqueous solution into heptane by the NHBu2/CO2 system. Partial hydrolysis (H2O/Ln molar ratio = ½ ) of N,N-di-iso-propylcarbamato complexes of neodymium, europium, gadolinium and terbium, [Ln(O2CNiPr2)3], yielded the derivatives [Ln2(CO3)(O2CNiPr2)4] (Ln = Nd, 4, Eu, 5, Gd, 6). Exhaustive hydrolysis of [Ln(O2CNR2)3] (Ln = Nd, Tb, R = Bu; Ln = Eu, Gd, R = iPr, Bu) produced hydrated lanthanide carbonates, Ln2(CO3)3 n H2O. For sake of comparison with a block d metal, the exhaustive hydrolysis of two copper(II) carbamato complexes, [Cu(O2CNEt2)2(NHEt2)]2 and [Cu(O2CNiPr2)2], was carried out with formation in both cases of the hydrated basic carbonate Cu2(OH)2(CO3)nH2O. The exhaustive hydrolysis of mixtures of cerium and lanthanum or cerium and terbium N,N-dibutylcarbamato complexes allowed the preparation of mixed oxides containing the two metals in the desired molar ratio, via the intermediate formation of the corresponding mixed carbonates

A convenient preparation of La2CuO4 from molecular precursors

Exhaustive hydrolysis of a mixture of [La4(CO3)(O2CNBu2)10] and [Cu(O2CNBu2)(py∗)2] (py∗ = 4-dimethylamino pyridine) in molar ratio 1/2 corresponding to a La/Cu molar ratio 2/1 was carried out in toluene at room temperature. The carbamato derivatives of lanthanum and copper can be easily prepared by extraction of the metal ions from aqueous solution into heptane by the NHBu2/CO2 system, according to a method previously reported. The copper precursor was selected among a number of derivatives in respect of its easy tractability. The tetragonal modification T’ of La2CuO4 was obtained by treatment at 600 °C of the intermediate mixed carbonate. The thermal treatment of T’-La2CuO4 at 850 °C, followed by cooling down to room temperature, afforded the orthorhombic modification of the mixed oxide

Synthesis and reactivity of cytotoxic platinum(II) complexes of bidentate oximes: a step towards the functionalization of bioactive complexes

Two new platinum(II) complexes bearing triphenylphosphine and bidentate oxime ligands [Pt(Cl)(PPh3){(κ2-N,O)-(1{C(R)=N(OH)-2(O)C10H6})}] (R = H, Me) were synthesized in good yields from trans-[PtCl(μ-Cl)(PPh3)]2. The structure of [Pt(Cl)(PPh3){(κ2-N,O)-(1{CH=N(OH)-2(O)C10H6})}] was determined by single-crystal X-ray diffraction. Both complexes showed good antiproliferative properties in vitro against HeLa, A2780, and A2780cis cancer cell lines. They reacted cleanly with alkylating agents in the presence of aqueous bases under phase-transfer catalysis conditions to afford the corresponding O-alkylation products [Pt(Cl)(PPh3){(κ2-N,O)-(1{HC=N(OR′)-2(O)C10H6})}] [R′ = CH2CH2Cl, CH2Ph, (CH2)4Br] in good yields