Fraser Hector W L, Nichol Gary S, Velmurugan Gunasekaran, Rajaraman Gopalan, Brechin Euan K
EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, Scotland, UK.
Dalton Trans. 2017 Jun 6;46(22):7159-7168. doi: 10.1039/c7dt01197k.
A series of di-alkoxo bridged Cr(iii) dimers have been synthesised using pyridine alcohol ligands. The structures fall into four general categories and are of formula: [Cr(OMe)(pic)]·½MeOH·½EtO (1), [Cr(hmp)(pic)X] (where X = Cl (2), Br (3)), [Cr(L)Cl(A)]·2S (where L = hmp, A = HO and S = EtO (4); L = hmp, A = pyridine and S = pyridine (5); L = hmp, A = 4-picoline and no S (6); L = hep, A = HO and S = MeCN (7)), and [Cr(hmp)(hmpH)Cl]·MeCN (8). Direct current (DC) magnetic susceptibility measurements show relatively weak antiferromagnetic exchange interactions between the Cr(iii) centres with J values <|15| cm in all of the complexes measured. DFT calculations performed on complexes 1-8 reproduce both the sign and strength of the exchange interactions found experimentally, and confirm that the magnitude and sign of the J value is strongly dependent upon the orientation of the dihedral angle formed between the bridging CrO plane and the O-R vector of the bridging group (θ), and the Cr-O-Cr-O dihedral angle (ψ).
利用吡啶醇配体合成了一系列二烷氧基桥连的Cr(iii)二聚体。这些结构可分为四大类，其通式为：[Cr(OMe)(pic)]·½MeOH·½EtO (1)，[Cr(hmp)(pic)X]（其中X = Cl (2)，Br (3)），[Cr(L)Cl(A)]·2S（其中L = hmp，A = HO且S = EtO (4)；L = hmp，A =吡啶且S =吡啶(5)；L = hmp，A = 4-甲基吡啶且无S (6)；L = hep，A = HO且S = MeCN (7)），以及[Cr(hmp)(hmpH)Cl]·MeCN (8)。直流（DC）磁化率测量表明，在所有测量的配合物中，Cr(iii)中心之间的反铁磁交换相互作用相对较弱，J值<|15| cm。对配合物1 - 8进行的密度泛函理论（DFT）计算再现了实验中发现的交换相互作用的符号和强度，并证实J值的大小和符号强烈依赖于桥连CrO平面与桥连基团的O - R向量（θ）以及Cr - O - Cr - O二面角（ψ）形成的二面角的取向。
