School of Chemistry , University of Melbourne , Melbourne , VIC 3010 , Australia.
UdR INSTM and Department of Chemistry "U. Schiff" , University of Florence , 50019 Sesto Fiorentino , FI , Italy.
Inorg Chem. 2019 Apr 1;58(7):4230-4243. doi: 10.1021/acs.inorgchem.8b03291. Epub 2019 Mar 20.
The family of complexes of general formula [Co(Me tpa)(Xdiox)] (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to successive methylation of the 6-position of the pyridine rings; X = Br, Cl, H, 3,5-Me, 3,5- tBu; diox = dioxolene) was investigated by density functional theory (DFT) calculations to predict the likelihood of valence tautomerism (VT). The OPBE functional with relativistic and solvent corrections allowed accurate reproduction of trends in spin-state energetics, affording the prediction of VT in complex [Co(Metpa)(Brdiox)] (1). One-electron oxidation of neutral precursor [Co(Metpa)(Brcat)] (1) enabled isolation of target compounds 1(PF) and 1(BPh). Solution variable-temperature UV-vis absorption and Evans method magnetic susceptibility data confirm DFT predictions that 1 exists in a temperature-dependent valence tautomeric equilibrium between low-spin Co(III)-catecholate and high-spin Co(II)-semiquinonate forms. The solution VT transition temperature of 1 is solvent-tunable with critical temperatures in the range of 291-359 K for the solvents measured. Solid-state magnetic susceptibility measurements of 1(PF) and 1(BPh) reveal the onset of VT transitions above room temperature.
研究了通式为[Co(Me tpa)(Xdiox)]的配合物家族（tpa = 三（2-吡啶基甲基）胺，n = 0-3 对应于吡啶环 6 位的连续甲基化；X = Br、Cl、H、3,5-Me、3,5- tBu；diox = 二氧戊环），通过密度泛函理论（DFT）计算预测了价态互变异构（VT）的可能性。具有相对论和溶剂校正的 OPBE 函数准确地再现了自旋态能学的趋势，从而能够预测配合物[Co(Metpa)(Brdiox)]（1）中的 VT。中性前体[Co(Metpa)(Brcat)]（1）的单电子氧化能够分离出目标化合物 1(PF)和 1(BPh)。溶液变温 UV-vis 吸收和 Evans 方法磁化率数据证实了 DFT 的预测，即 1 存在低自旋 Co(III)-儿茶酚和高自旋 Co(II)-半醌酸盐形式之间的温度依赖的价态互变异构平衡。1 的溶液 VT 转变温度可通过溶剂调节，在所测量的溶剂中，临界温度范围为 291-359 K。1(PF)和 1(BPh)的固态磁化率测量表明 VT 转变在室温以上开始。
