•Trans-bis(salicylaldiminato)platinum(II) platform with polymethylene-vaulted structures.•An unprecedented linker-dependent chromogenic control of emission.•A clear mechanistic rationale based on DFT and TD-DFT calculations.The emission wavelengths of polymethylene-vaulted trans-bis(salicylaldiminato)platinum(II) complexes 1a–f (n=8–13) in a 2-MeTHF glass state at 77 K clearly vary with the length of the linker, such that a very regular hypsochromic shift from yellow to green is observed upon transitioning from octamethylene (1a, n=8) to tridecamethylene (1f, n=13) linkages. This structure-dependent chromism is explained based on DFT and TD-DFT calculations comparing the T1–S0 gaps in optimized 1a, 1c (n=10) and 1e (n=12) structures.

trans-Bis[1-(2-phenoxy)-imidazol-2-ylidene-C2,O]platinum(II) complex bearing a dodecamethylene bridge (1) was synthesized and characterized by 1H, 13C NMR, COSY, NOESY, FT-IR, high-resolution mass spectroscopy, and single crystal X-ray diffraction. X-ray and 2D-NMR analyses revealed that complex 1 has a characteristic syn-conformation in both the solid and solution states, where cofacial phenoxy-NHC ligands are folded and fixed under strong restriction by the vaulted structure. A crystal of 1 obtained from EtOH exhibits weak blue phosphorescence under UV excitation at 320 nm.The first trans-bis[1-(2-phenoxy)-imidazol-2-ylidene-C2,O]platinum(II) complex (1) was synthesized by utilizing high conformational restriction due to the vaulted structure. Complex 1 has a characteristic syn-conformation in both the solid and solution states, where cofacial phenoxy-NHC ligands are folded and fixed under strong restriction by the vaulted structure.Highlights► The first trans-ligating bis(o-phenoxy-NHC)Pt(II) complex ► Vaulted structure with polymethylene spacer ► Extremely syn-bent conformation maintained in both the solid and solution states

The synthesis, structure, and conformational mobility of a trans-bis(aminophenolato)platinum(II) complex bearing a dodecamethylene bridge, [Pt(L)] (1) [H2L = N,N′-Dimethyl-N,N′-bis(2-hydroxyphenylmethyl)dodecane-1,12-diamine] are described. The 2D NMR and X-ray diffraction analysis revealed that the complex has a “reversed U”-shaped syn conformation in the solution state, which is mainly due to steric congestion of the vaulted structure and hydrogen bonding at the bis[(o-aminomethyl)phenolato] coordination site, while the complex unit is packed in the crystalline state with “Z-shaped” anti-conformation due to highly regulated molecular arrangement by 3D CH-π and hydrogen bonding interactions.

The aerobic oxidation of alcohols in water can be performed efficiently in the presence of a catalytic amount of the water-soluble diruthenium complex Ru2(μ-OAc)3(μ-CO3) under an atmospheric pressure (1 atm) of O2.