Electronic Structures and Spectroscopic Properties of [Pt(CNMe)₂(CN)₂]n (n = 1–4): A Theoretical Exploration of Promising Phosphorescent Materials

The structures of [Pt(CNMe) 2 (CN) 2 ] n ( n = 1–4) in the ground states (S 0 ) and lowest‐energy triplet excited states (T 1 ) were calculated by using the second‐order Møller–Plesset perturbation (MP2) and density functional theory (DFT) methods, respectively. The MP2 results show that the formation of the dimer causes a significant red shift in emission energy, and the frequency calculations reveal that a weak metal–metal interaction exists in the S 0 state, which is greatly enhanced in the 3 [d σ* p σ ] excited state. The aggregation of [Pt(CNMe) 2 (CN) 2 ] n ( n = 1–4) was explored by using the slate‐type VWN functional in the DFT method. The 3 B u → 1 A g transition in the dimer at 509 nm corresponds to the experimental higher‐energy emission at 530 nm in CH 3 CN solution, while the 3 A′→ 1 A′ transitions in the trimer and tetramer at 557 and 650 nm, respectively, are responsible for the low‐energy emission at 584 nm observed experimentally. The analyses of the Wiberg bond indices for the Pt–Pt bond indicate that the dimer may be the most stable form in solution and that the oligomer species ( n = 3 and 4) can be treated as a special dimer in which the excess z electron ligand is bonded to the Pt atoms of the central dimer.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)