Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan.
Dalton Trans. 2013 Apr 14;42(14):4809-21. doi: 10.1039/c2dt32685j.
Vapochromic complexes Au(im(CH(2)py)(2))(2)(Cu(MeCN)(2))(2) 1, Au(im(CH(2)py)(2))(2)(Cu(MeOH))(2) 2 and Au(im(CH(2)py)(2))(2)(Cu(H(2)O))(2) 3 were theoretically investigated. The Au–Cu distances of 1 and 2 (4.631 Å and 2.767 Å, respectively) optimized by the SCS-MP2 method in this work agree with the literature experimental values (4.591 Å and 2.792 Å). Their structural features are explained by computational results: (i) in 1, two MeCN molecules coordinate with the Cu center, because of the strong coordination ability of MeCN, to afford a four-coordinate tetrahedral-like Cu center. This geometry needs a long Au–Cu distance. (ii) In 2 and 3, only one MeOH or H(2)O molecule coordinates with the Cu center because of their weak coordination abilities, to afford a three-coordinate planar Cu center. Because the three-coordinate Cu center is flexible, the Au–Cu distance becomes short due to the Au–Cu metallophilic interaction, the strength of which is 5.3 kcal mol(−1) at the SCS-MP2 level. The emission energies of 1, 2 and 3 (2.62, 2.40 and 2.38 eV, respectively) calculated here by the B3PW91 agree with their literature experimental values (2.68, 2.47, and 2.39 eV). The lowest energy triplet excited state (T(1)) is assigned as the excitation from the Cu d to the pyridine π* orbital in 1 and that from the Au–Cu 5d–3d anti-bonding MO to the Au–Cu 6p–4sp bonding MO in 2 and 3. As a result, the emission energy from the T(1) to the ground state is different between these compounds. The difference in Au–Cu distance is one of the important factors for the differences in emission energy and assignment between 1 and others (2 and 3). The vapochromism of these compounds arises from the difference in Au–Cu distance which is determined by the balance between the strengths of the coordination of a gas molecule and the Au–Cu metallophilic interaction; in other words, the Au–Cu heterometallophilic interaction is important for the vapochromic activity of the complex.
本文理论研究了变色配合物 Au(im(CH(2)py)(2))(2)(Cu(MeCN)(2))(2) 1、Au(im(CH(2)py)(2))(2)(Cu(MeOH))(2) 2 和 Au(im(CH(2)py)(2))(2)(Cu(H(2)O))(2) 3。本工作中通过 SCS-MP2 方法优化的 1 和 2 的 Au-Cu 距离（分别为 4.631 Å 和 2.767 Å）与文献实验值（4.591 Å 和 2.792 Å）相符。其结构特征可以通过计算结果来解释：（i）在 1 中，由于 MeCN 的强配位能力，两个 MeCN 分子与 Cu 中心配位，形成四配位的四面体 Cu 中心。这种几何形状需要较长的 Au-Cu 距离。（ii）在 2 和 3 中，由于 MeOH 或 H(2)O 的配位能力较弱，只有一个 MeOH 或 H(2)O 分子与 Cu 中心配位，形成三配位的平面 Cu 中心。由于三配位的 Cu 中心是灵活的，由于 Au-Cu 金属亲合相互作用，Au-Cu 距离变短，其强度在 SCS-MP2 水平为 5.3 kcal mol(−1)。本文通过 B3PW91 计算的 1、2 和 3 的发射能（分别为 2.62、2.40 和 2.38 eV）与文献实验值（2.68、2.47 和 2.39 eV）相符。最低能量三重态激发态（T(1)）被分配为 1 中从 Cu d 到吡啶 π* 轨道的激发，以及 2 和 3 中从 Au-Cu 5d-3d 反键 MO 到 Au-Cu 6p-4sp 成键 MO 的激发。因此，这些化合物的 T(1)到基态的发射能不同。在发射能和归属方面，1 和其他化合物（2 和 3）之间的差异之一是 Au-Cu 距离的差异。这些化合物的变色性源于 Au-Cu 距离的差异，这取决于气体分子配位强度与 Au-Cu 金属亲合相互作用之间的平衡；换句话说，Au-Cu 杂金属亲合相互作用对配合物的变色活性很重要。
