Laboratory of Inorganic and General Chemistry, Department of Chemistry, University of Ioannina, 451 10 Ioannina, Greece.
Inorg Chem. 2012 Feb 20;51(4):2541-59. doi: 10.1021/ic202497j. Epub 2012 Jan 9.
The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula c-M(3)(μ(2)-X)(3)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 Å at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 Å) and Ag···C (3.44 Å). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems.
苯-三核铜（I）和银（I）三卤化物柱状二元堆积物的分子和电子结构、稳定性、键合特征、磁各向异性和吸收光谱，具有通式 c-M(3)(μ(2)-X)(3)(C(6)H(6))(m) (M = Cu，Ag；X = 卤素；n，m ≤ 2)，已通过电子结构计算方法进行了研究。c-M(3)(μ(2)-X)(3) 簇与一个和两个苯分子的相互作用生成 1:1 和 1:2 二元堆积物，而两个 c-M(3)(μ(2)-X)(3) 簇与一个苯分子相互作用则形成苯夹心 2:1 堆积物。在所有二元堆积物中，交替的 c-M(3)(μ(2)-X)(3) 和苯组成部分的平面采用几乎平行的取向。在 B97D/Def2-TZVP 水平下，在苯和近 c-M(3)(μ(2)-X)(3) 金属簇的质心之间发现的分离距离在 2.97-3.33 Å 范围内，表明存在π···π堆积相互作用模式，因为质心分离距离非常接近 Cu···C 的范德华半径之和（3.10 Å）和 Ag···C（3.44 Å）。在 SSB-D/TZP 水平下的能量分解分析（EDA）表明，c-M(3)(μ(2)-X)(3)···C(6)H(6) 相互作用中的主导项来自色散力和静电力，而共价相互作用预计可以忽略不计。另一方面，电荷分解分析（CDA）表明，从 C(6)H(6) 向 c-M(3)(μ(2)-X)(3) 簇转移的电荷非常小，因此反映出较弱的π-碱/π-酸相互作用，这进一步得到了各自的静电势的证实，并且总偶极矩向量指向 c-M(3)(μ(2)-X)(3) 簇的金属环的中心。通过 TD-DFT 计算模拟的所有芳香族柱状二元堆积物的吸收光谱在 UV 区域显示出强烈的吸收。对模拟吸收光谱的主要特征进行了彻底分析，并给出了贡献电子跃迁的归属。通过 NICS(zz)-扫描曲线评估的二元堆积物的磁各向异性表明，在与芳香苯分子相互作用时，无机环的各向异性增强。值得注意的是，苯环的各向异性略有增强，特别是在相互作用环之间的区域，这可能是由于相互作用的芳香环系统的抗磁性环电流的叠加（耦合）。
