Schuman Ashley J, Raghavan Adharsh, Banziger Susannah D, Song You, Hu Zhao-Bo, Mash Brandon L, Williams Andrew L, Ren Tong
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
Inorg Chem. 2021 Apr 5;60(7):4447-4455. doi: 10.1021/acs.inorgchem.0c03224. Epub 2021 Mar 12.
The synthesis and structural, electrochemical, spectroscopic, and magnetic characterizations of Cr(HMC) catecholate and semiquinonate complexes are reported herein, where HMC is 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. [Cr(HMC)(Cat)] complexes (Cat = catecholate, []; tetrachlorocatecholate, []; and 3,5-di--butylcatecholate, []) were prepared from the reaction between appropriate catechol and [Cr(HMC)Cl]Cl reduced by zinc. Chemical oxidation of [] by FcPF resulted in -[Cr(HMC)(SQ)] ([], SQ = 3,5-di--butylsemiquinonate). Single crystal X-ray diffraction studies revealed the chelation of the Cat/SQ ligand around the Cr metal center and confirmed the Cat/SQ nature of the ligands. Reversible oxidations of Cat to SQ were observed in the cyclic voltammograms of []-[], while the Cr center remains redox inactive. The absorption spectrum of the SQ complex [] exhibits an intense spin-forbidden transition in solution. Time-delayed phosphorescence spectra recorded at 77 K revealed that all catecholate complexes emit from the E state, while [] also emits from the T state. Temperature-dependent magnetic susceptibility measurements indicate the Cat complexes exist as = 3/2 systems, while the SQ complex behaves as an = 1 system, resulting from strong antiferromagnetic coupling of the = 3/2 Cr center with the = 1/2 SQ radical. Density functional theory (DFT) shows the similarities between the SOMOs of [] and [] and differences in their LUMOs in the ground state.
本文报道了铬（HMC）儿茶酚盐和半醌配合物的合成及其结构、电化学、光谱和磁性表征，其中HMC为5,5,7,12,12,14-六甲基-1,4,8,11-四氮杂环十四烷。[Cr（HMC）（Cat）]配合物（Cat = 儿茶酚盐，[]；四氯儿茶酚盐，[]；3,5-二叔丁基儿茶酚盐，[]）由适当的儿茶酚与经锌还原的[Cr（HMC）Cl]Cl反应制备而成。[]经FcPF化学氧化得到-[Cr（HMC）（SQ）]（[]，SQ = 3,5-二叔丁基半醌）。单晶X射线衍射研究揭示了Cat/SQ配体在Cr金属中心周围的螯合作用，并证实了配体的Cat/SQ性质。在[]-[]的循环伏安图中观察到Cat向SQ的可逆氧化，而Cr中心保持氧化还原惰性。SQ配合物[]的吸收光谱在溶液中表现出强烈的自旋禁阻跃迁。在77 K下记录的时间分辨磷光光谱表明，所有儿茶酚盐配合物均从E态发射，而[]也从T态发射。变温磁化率测量表明，Cat配合物以S = 3/2体系存在，而SQ配合物表现为S = 1体系，这是由于S = 3/2的Cr中心与S = 1/2的SQ自由基之间存在强反铁磁耦合作用。密度泛函理论（DFT）表明[]和[]的单占据分子轨道（SOMO）之间存在相似性，且它们基态的最低未占分子轨道（LUMO）存在差异。
