Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata 700 009, India.
Departament de Química Inorgànica I Orgànica, Secció Inorgànica and Institut de Nanosciència I Nanotecnologia (IN2UB), Martíi Franqués 1-11, 08028, Barcelona, Spain.
Dalton Trans. 2020 Aug 18;49(32):11268-11281. doi: 10.1039/d0dt00952k.
Five new heterometallic Cu(ii)-Mn(ii) discrete trinuclear complexes, [(CuL)2Mn(CH3COO)2] (1), [(CuL)2Mn(NO3)2] (2), [(CuL)2Mn(C6H5COO)(H2O)]Cl (3), [(CuL)2Mn((p-OH)C6H5COO)(H2O)]ClO4 (4) and [(CuL)2Mn(HCOO)(H2O)]ClO4 (5), have been synthesized using a metalloligand, CuL derived from an N2O2 donor Schiff base, H2L (N,N'-bis(α-methylsalicylidene)-1,3-propanediamine). Single-crystal structural analyses reveal that all five complexes have a common [(CuL)2Mn] core, where two terminal metalloligands, CuL, are connected to the central metal ion, Mn(ii), via double phenoxido bridges. Among the complexes, 1 and 2 possess linear structures where the terminal Cu(ii) atoms are bridged to the central Mn(ii) atoms by acetate and nitrate ions, respectively along with the double phenoxido bridges, whereas 3, 4 and 5 have bent structures in which the respective anionic coligands, benzoate, p-hydroxybenzoate and formate ions are coordinated only to central Mn(ii) in monodentate fashion along with a water molecule that completes its hexa-coordinated geometry. Among the complexes, 1, 3, 4 and 5 show quite high bio-mimicking catecholase-like activity for the aerial oxidation of 3,5-di-tert-butylcatechol with turnover numbers (Kcat) of 139 h-1, 439 h-1, 348 h-1 and 730 h-1, respectively, whereas complex 2 is practically inactive towards this reaction. The presence of the coordinated water molecule to Mn(ii) in the bent complexes, 3-5, appears to be responsible for their high catalytic activity and the difference in their activity may be attributed to steric crowding due to the anionic coligand, whereas the inactivity of 2 seems to be associated with the low basicity of the nitrate ion. The temperature-dependent dc molar magnetic susceptibility measurements reveal that complexes 1-5 are antiferromagnetically coupled with the exchange coupling constants (J) = -8.54 cm-1, -11.50 cm-1, -19.83 cm-1, -10.65 cm-1 and -10.27 cm-1 for 1, 2, 3, 4 and 5 respectively as is expected from the Cu-O-Mn bridging angles.
五个新的异金属 Cu(ii)-Mn(ii)离散三核配合物，[(CuL)2Mn(CH3COO)2]（1）、[(CuL)2Mn(NO3)2]（2）、[(CuL)2Mn(C6H5COO)(H2O)]Cl（3）、[(CuL)2Mn((p-OH)C6H5COO)(H2O)]ClO4（4）和[(CuL)2Mn(HCOO)(H2O)]ClO4（5），已经通过一个金属配体 CuL 合成，CuL 由一个 N2O2 供体席夫碱 H2L（N，N'-双（α-甲基水杨醛）-1,3-丙二胺）衍生而来。单晶结构分析表明，所有五个配合物都具有一个共同的[(CuL)2Mn]核心，其中两个末端金属配体 CuL 通过双酚氧桥与中心金属离子 Mn(ii)相连。在这些配合物中，1 和 2 具有线性结构，其中末端 Cu(ii)原子通过乙酸盐和硝酸盐离子分别与中心 Mn(ii)原子桥接，同时还有双酚氧桥，而 3、4 和 5 具有弯曲结构，其中各自的阴离子配位体苯甲酸根、对羟基苯甲酸根和甲酸盐离子仅以单齿配位方式与中心 Mn(ii)配位，并与一个水分子一起完成其六配位几何结构。在这些配合物中，1、3、4 和 5 对 3,5-二叔丁基儿茶酚的空气氧化表现出相当高的类儿茶酚酶活性，其周转率（Kcat）分别为 139 h-1、439 h-1、348 h-1 和 730 h-1，而 2 对该反应几乎没有活性。弯曲配合物 3-5 中 Mn(ii)的配位水分子的存在似乎是它们高催化活性的原因，而它们活性的差异可能归因于阴离子配位体的空间位阻，而 2 的无活性似乎与硝酸盐离子的低碱性有关。温度依赖的 dc 摩尔磁化率测量表明，配合物 1-5 是反铁磁耦合的，交换耦合常数（J）分别为-8.54 cm-1、-11.50 cm-1、-19.83 cm-1、-10.65 cm-1 和-10.27 cm-1，这与预期的 Cu-O-Mn 桥接角一致。
