[en] New platinum(II) complexes with asymmetrically substituted chiral diamine ligands A₂PtX₂, (A₂=NH₂CH(CH₃)CH₂NH(c-C₅H₉) (apcpa), NH₂CH(CH₃)CH₂NH(c-C₆H₁₁) (apcha); X₂=2Cl, isopropylidenmalonate (IPM), 1,1'-cyclobutandicarboxylate (CBDCA) have been synthesized and characterized by means of elemental analyses, infrared and NMR spectroscopies, and X-ray crystallography. The crystal structures of (S-apcha)Pt[CBDCA]·3H₂O (orthorhombic, P2₁2₁2(No. 18), a=6.926(3), b=15.243(3), c=19.319(4) A, V=2039.5(10) A³, Z=4, R=0.072) and (S-apcha)Pt[IPM]·2.5H₂O (monoclinic, P2/c(No. 13), a=9.882(1), b=18.502(1), c=22.056(1) A, V=4032.8(5) A³, Z=8, R=0.093) exhibit that the platinum atoms achieve a typical square planar arrangement with two nitrogen atoms in cis position and with the chiral center retained. The spectroscopic data disclose that these platinum complexes are stable and their molecular structures are retained in aqueous solution. Among these platinum complexes, the asymmetric diamine-Pt(II) complexes with chloride leaving group exhibit high in vivo activity comparable to cisplatin against leukemia L1210 cell line

[en] A series of (diamine)isopropylidenmalonatoplatinum(II) complexes and the oxidation products, (diamine)Pt(OOC)₂C=C(CH₃)₂(X)₂, (diamine=ethylenediamine(en), 1,2-diaminopropan(dap), N-methylethylenediamine(men); X=OH, OCOCH₃, OCOCF₃), have been prepared, and their interaction with guanosine-5'-monophosphate (5'-GMP) have been examined by means of ¹H NMR spectroscopy. The present platinum(II) complexes have shown to interact with 5'-GMP through N7 coordination in two consecutive steps in a similar way as with cisplatin, but no interaction between the present platinum(IV) complexes and 5'-GMP was observed. However, in the presence of ascorbic acid, the platinum(IV) complexes have been found to interest with 5'-GMP with the reation rate depending on their reduction rate

[en] Novel platinum(IV) complexes with asymmetric chiral diamine ligands cis, cis, trans-A₂PtCl₂(X)₂ (X=OH, OCOCH₃, OCOC₂H₅, A₂=NH₂CH(CH₃)CH₂NH(c-C₆H₁₁)(apcha), NH₂CH(CH₃)CH₂NH(c-C₅H₉)(apcpa)) have been prepared. One of the platinum(IV) complexes, (apcpa)PtCl₂(OCOC₂H₅)₂(6), was subjected to X-ray crystallographic analysis. The crystal structure of (apcpa)PtCl₂(OCOC₂H₅)₂ (monoclinic, P2₁ (No.4), a=9.1391(1), b=22.2517(1), c=10.0687(1) A, β=109.105(1) .deg. , V=1934.80(3) A³, Z=4, R₁=0.0532) exhibits that the platinum atom achieves a typical octahedral arrangement with two nitrogen atoms in cis positions and two carboxylato group in trans positions. The spectroscopic data disclose that these platinum(IV) complexes are stable and their molecular structures are retained in aqueous solution. The title complexes are highly cytotoxic in vitro but do not exhibit oral anticancer activity in vivo

[en] Increasing interest in coordination and organometallic polymers lies in the various intriguing properties of well-designed inorganic polymer materials. A variety of attempts have been made to synthesize multidentate ligands which can bridge various metal centers. Ambidentate poly(triazolyl) borate ligands [H_nB(tz)_4-n]. (n = 1 and 2, tz = 1,2,4-triazol-1-yl) are good candidates for multidimensional network topologies

[en] We have developed molecular switching system triggered by oxalate anion operating on platinum square planar coordination plane by controlling well-known alkyl inversion process on nitrogens. This work shows that oxalate anion disturbs the thermodynamic equilibrium between syn and aniti conformer and induces the syn conformer to be produced in excess. Thus oxalate may be regarded as a trigger that bring about the conformational change of complex 1. This behavior might be exploited to develop sensors for the kidney stone disease-related oxalate anions. A molecular conformational switching has been of growing interest in association with molecular electronics, machines and sensors. External stimuli such as a transition metal, light, a redox reaction, pH variation and guest molecules were used to control the thermodynamic equilibrium between the conformers. For example, complexation with lewis acid, TiCl₄, changes the conformation of arene-dicarboxamide from syn to anti atropisomer. The specially designed ligand is programmed to have syn conformer by the application of the transition metal complex PdCl₂(PhCN)₂. N-Alkyl-substituted-ethylenediamine complexes of platinum(II) are well known to adopt syn and anti conformers which are inter-converted fast in aqueous solutions. We have been interested in developing a conformational switching system by exploiting this behavior, thus designed complex with two uryl groups which are well known to bind carboxylates. We speculated that the thermodynamic ratio of syn to anti conformer of would be influenced by a suitable dicarboxylate anion such as oxalate which is a biologically important anion