On Mixed‐Valence Dinuclear PtII, PtIII Nucleobase Complexes Derived from cis‐Diamineplatinum(II): Effect of steric bulk of amine ligands on the Pt‐oxidation state

Peilert, Matthias; Erxleben, Andrea; Lippert, Bernhard

doi:10.1002/zaac.19966220212

Cited by 12 publications

(5 citation statements)

References 49 publications

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“…Generally, the distances between the adjacent platinum atoms in 6 , 9 , and 11 are shorter than a double van der Waals radius for Pt [1.72 × 2 = 3.44 Å]. Compared to the reported Pt···Pt distances in the platinum(II) dimeric complexes featuring two bridging ligands, e.g., (i) α-pyridonate [2.88–2.90 Å], (ii) 1-methyluracilate or 1-methylthyminate [2.927–2.986 Å], (iii) amidate [2.993–3.060 Å], (iv) amidinate [3.381 Å], and (v) carboxylate [2.952–2.990 Å], the Pt···Pt distances in 6 and 11 correspond to a rather weak nonbonded interaction between the platinum centers. On the contrary, the Pt···Pt distance in 9 is one of the shortest known for platinum(II) dimers.…”

Section: Resultsmentioning

confidence: 99%

Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural, and in Vitro Anticancer Activity Studies

et al. 2012

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Novel platinum complexes of trans geometry [PtCl(2){(Z)-R(H)C═NOH}(2)] [R = Me (1), Et (3)] and [PtCl(2){(E)-R(H)C═NOH}{(Z)-R(H)C═NOH}] [R = Me (2), Et (4)] as well as the classic trans-[PtCl(2)(R(2)C═NOH)(2)] [R = Me, Et] were reacted with an equivalent amount of silver acetate in acetone solution at ambient temperature, resulting in formation of unprecedented head-to-tail-oriented oximato-bridged dimers [PtCl{μ-(Z)-R(H)C═NO}{(Z)-R(H)C═NOH}](2) [R = Me (5), Et (7)], [PtCl{μ-(Z)-R(H)C═NO}{(E)-R(H)C═NOH}](2) [R = Me (6), Et (8)], and [PtCl(μ-R(2)C═NO)(R(2)C═NOH)](2) [R = Me (9), Et (10)], correspondingly. The dimeric species feature a unique six-membered diplatinacycle and represent the first example of oxime ligands coordinated to platinum via the oxygen atom. All complexes were characterized by elemental analyses, electrospray ionization mass spectrometry, IR and multinuclear ((1)H, (13)C, and (195)Pt) NMR spectroscopy, as well as X-ray diffraction in the cases of dimers 6 and 9. Furthermore, the crystal and molecular structures of a trimeric oximato-bridged complex 11 comprising three platinum units connected in a chain way were established. The cytotoxicity of both dimers and the respective monomers was comparatively evaluated in three human cancer cell lines: cisplatin-sensitive CH1 cells as well as cisplatin-resistant SW480 and A549 cells, whereupon structure-activity relationships were drawn. Thus, it was found that dimerization results in a substantial (up to 7-fold) improvement of IC(50) values of (aldoxime)Pt(II) compounds, whereas for the analogous complexes featuring ketoxime ligands the reverse trend was observed. Remarkably, the novel dimers yielded no cross-resistance with cisplatin in SW480 cells, exhibiting up to 2-fold enhanced cytotoxicity in comparison with the CH1 cell line and thereby possessing a promising potential to overcome resistance toward platinum anticancer drugs. The latter point was also confirmed by investigating the potency of apoptosis induction in the case of one monomer as well as one dimer; the investigated complexes proved to be strong apoptotic agents which could induce cell death even in the cisplatin-resistant SW480 cell line.

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Section: Resultsmentioning

confidence: 99%

Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural, and in Vitro Anticancer Activity Studies

et al. 2012

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“…In general, paramagnetic monomeric platinum(III) complexes are very rare , because trivalent platinum has a strong tendency to dimerization that quenches spins of unpaired electrons . Few examples of paramagnetic mixed-valence Pt II −Pt III species are also known. , The oxidized 7 seems to have limited stability in solution, since its EPR signal disappears when the solution is stored at room temperature for a few hours.…”

Section: Resultsmentioning

confidence: 99%

“…50 Few examples of paramagnetic mixedvalence Pt II -Pt III species are also known. 51,52 The oxidized 7 seems to have limited stability in solution, since its EPR signal disappears when the solution is stored at room temperature for a few hours.…”

Section: Resultsmentioning

confidence: 99%

Diastereoselective Assembling of 21-C-Alkylated Nickel(II) Complexes of Inverted Porphyrin on a Platinum(II) Template

Chmielewski

Schmidt

2004

Inorg. Chem.

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Reaction of 21-C-methyl and 21-C-benzyl nickel(II) complexes of inverted meso-tetratolylporphyrin with platinum(II) dichloride or its bis(benzonitrile) complex yields a chloroplatinum(II) species containing two nickel(II) carbaporphyrinoids in a cis arrangement. One of the carbaporphyrinoids coordinates to the platinum ion with the external nitrogen while the other is bound with the external nitrogen and one ortho-carbon of the adjacent meso-aryl ring. The reaction is highly chemoselective. (1)H and (13)C NMR experiments in solution show the diastereoselectivity of the reaction. Single-crystal X-ray data confirm the presence of the diastereomer with opposite configurations of the Ni(II)-coordinated carbons in the subunits of the dimer. Cyclovoltammetric measurements reveal an anodic shift of the nickel(II) oxidation potentials of dimers with respect to those of the parent monomers and two different reduction couples. Reaction of unsubstituted inverted porphyrin with Pt(PhCN)(2)Cl(2) in chlorobenzene yields a monomeric platinum(II) complex of inverted porphyrin. This complex displays a markedly upfield (195)Pt NMR shift compared to tetraphenylporphyrinatoplatinum(II). Under strongly basic conditions deprotonation of the external nitrogen of inverted porphyrin and both electrochemical and chemical oxidation of platinum(II) center are observed.

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“…Although it is felt that the species giving rise to the purple color might be a mixed-valence Pt compound, e.g. a Pt III Pt II compound, the EPR spectrum of a frozen purple solution does not display the typical characteristics of such compounds, namely a spectrum of approximately axial symmetry with g ⊥ ≈ 2.4−2.5 and g || ≈ 2. , Rather, its spectrum with two g values ( g 1 ≈ 2.26; g 2 ≈ 2.1) is reminiscent of a Cu II species as seen in Pt,Cu,Pt compounds, even though the typical splitting of g 1 into four components is not seen.…”

Section: Resultsmentioning

confidence: 99%

Diplatinum(III) Complexes with Four Bridging 1-Methylcytosinato Nucleobases Derived from a Mononucleartrans-(NH₃)₂Pt^IIComplex and Cu^II

et al. 2003

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A heteronuclear complex of composition trans-[(NH(3))(2)Pt(N4-1-MeC(-)-N3)(2)Cu(H(2)O)(2)](ClO(4))(2) (1a), with 1-MeC(-) = 1-methylcytosinate, has been prepared and characterized by X-ray crystallography. 1a (Cu,Pt) is a linkage isomer of a previously described compound with the two metals inverted (Pt,Cu). The intermetallic distances are significantly different in the two types of compounds, 2.6109(9) A in 1a, yet 2.49-2.56 A in several forms of the linkage isomer. When heated in water in the presence of air, 1a is converted in low yield into diplatinum(III) compounds [(H(3)N)Pt(1-MeC(-)-N3,N4)(4)Pt(NH(3))](2+) (2a) and [(H(2)O)Pt(1-MeC(-)-N3,N4)(4)Pt(NH(3))](2+) (2b), which were crystallized as ClO(4)(-) salts. In a modified procedure a third representative of this group of diplatinum(III) compounds, [(O(2)N)Pt(1-MeC(-)-N3,N4)(4)Pt](+) (2c) was isolated. All three compounds contain the four bridging 1-MeC ligands in a head,tail,head,tail arrangement with Pt-Pt distances (2.4516(7)-2.4976(9) A) that are the shortest ones among diplatinum(III) compounds containing nucleobases.

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On Mixed‐Valence Dinuclear Pt^II, Pt^III Nucleobase Complexes Derived from cis‐Diamineplatinum(II): Effect of steric bulk of amine ligands on the Pt‐oxidation state

Cited by 12 publications

References 49 publications

Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural, and in Vitro Anticancer Activity Studies

Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural, and in Vitro Anticancer Activity Studies

Diastereoselective Assembling of 21-C-Alkylated Nickel(II) Complexes of Inverted Porphyrin on a Platinum(II) Template

Diplatinum(III) Complexes with Four Bridging 1-Methylcytosinato Nucleobases Derived from a Mononucleartrans-(NH₃)₂Pt^IIComplex and Cu^II

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On Mixed‐Valence Dinuclear PtII, PtIII Nucleobase Complexes Derived from cis‐Diamineplatinum(II): Effect of steric bulk of amine ligands on the Pt‐oxidation state

Cited by 12 publications

References 49 publications

Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural, and in Vitro Anticancer Activity Studies

Novel Oximato-Bridged Platinum(II) Di- and Trimer(s): Synthetic, Structural, and in Vitro Anticancer Activity Studies

Diastereoselective Assembling of 21-C-Alkylated Nickel(II) Complexes of Inverted Porphyrin on a Platinum(II) Template

Diplatinum(III) Complexes with Four Bridging 1-Methylcytosinato Nucleobases Derived from a Mononucleartrans-(NH3)2PtIIComplex and CuII

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On Mixed‐Valence Dinuclear Pt^II, Pt^III Nucleobase Complexes Derived from cis‐Diamineplatinum(II): Effect of steric bulk of amine ligands on the Pt‐oxidation state

Diplatinum(III) Complexes with Four Bridging 1-Methylcytosinato Nucleobases Derived from a Mononucleartrans-(NH₃)₂Pt^IIComplex and Cu^II