960379-11-7Relevant academic research and scientific papers
Mononuclear and polynuclear copper(I) complexes with a new N,N′,S-donor ligand and with structural analogies to the copper thionein core
Gennari, Marcello,Lanfranchi, Maurizio,Cammi, Roberto,Pellinghelli, Maria Angela,Marchio, Luciano
, p. 10143 - 10152 (2007)
The N,N′,S-donor ligand 4-methoxy-3,5-dimethyl-2-((3-(2-(methylthio) phenyl)-1H-pyrazol-1-yl)methyl)pyridine (L) was prepared from 2-(chloromethyl)-4-methoxy-3,5-dimethylpyridine hydrochloride and 3-(2-(methylthio)phenyl)-1H-pyrazole. The Cu(I) complexes [CU 2(L)2CH3CN][CU(L)CH3CN](BF 4)3 (1), [Cu(L)PPh3]BF4 (2), and [Cu6(L)2(C6F5S)6] (3) were prepared and characterized by X-ray crystallography (PPh3 = triphenylphosphine, C6F5S- = pentafluorothiophenolate). The unit cell of compound 1 consists of cocrystallized mononuclear and dinuclear entities in which all of the copper atoms exhibit distorted tetrahedral coordination. Compound 2 is monomeric with L bound in the κ3-N,N′,S mode and a PPh3 molecule that completes the coordination environment. Compound 2 presents a fluxional behavior in CDCl3 solution due to the boat inversion of the six-membered N,N′ chelate ring (ΔH? = +43.6(3) kJ mol-1, ΔS? = -16(1) J mol-1 K-1). Crystallization of 3 in acetonitrile leads to a polynuclear structure that contains a CH3CN molecule coordinated to one of the copper atoms: [Cu6(L)2(C6F5S) 6CH3CN] (3a). The core of 3a partially resembles a {Cu4S6} adamantane-like moiety, the only difference being that the Cu-NCCH3 interaction leads to the opening of the cluster by disrupting a Cu-Cu interaction. Part of this assembly is found in the yeast metallothionein copper(I)-cysteinate core whose crystal structure has recently been reported. Two additional [Cu(L)]+ peripheral moieties interact with the cluster by means of bridging thiolates. ESI-mass spectrometry, conductivity measurements, and 1H/19F pulsed gradient spin echo (PGSE) NMR experiments suggest that 3a dissociates in acetonitrile solution: 3a + CH3CN → [Cu4(C6F 5S)6]2- + 2[Cu(L)CH3CN]+. The stability of the cluster with respect to the hypothetical mononuclear species, [Cu(L)(C6F5S)], is confirmed by DFT calculations (B3LYP), which illustrate the exergonic character of the reaction: 6[Cu(L′)(C6H5S)] → [Cu6(L′) 2(C6H5S)6] + 4L′ (ΔG298 = -58.6 kJ mol-1, where L′ and C 6H5S- are simplified models for L and C 6F5S-, respectively). The energetics pertinent to the ionic dissociation of the cluster in acetonitrile is computed using the polarizable continuum model (PCM) approach.
