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Abstract: A rhenium(I) complex ReL R,R (CO)3Cl (1) based on a chiral ligand, L R,R =(−)-4,5-pinene-2,2′-bipyridine [(6R)-5,6,7,8-tetrohedro-7,7-dimethyl-3-(2-pyridinyl)-6,8-methanoisoquinoline], was synthesized and characterized. The emission spectrum of 1 shows efficient dπ(Re)→π* (diimine) (MLCT) phosphorescence with a photoluminescence quantum efficiency of 0.035. The excited state lifetimes of Re(I) complex, measured in CH2Cl2 solution (1.82μs) and solid state (2.15μs) at room temperature, support the hypothesis of the MLCT character of the emitting state. Single crystal X-ray diffraction analyses show that complex 1 crystallizes in the chiral space group P21 of monoclinic system. The P–E hysteresis loop indicates its obvious ferroelectricity with the remnant polarization (P r) value of 0.17μC/cm2 at an applied field of 4.8kV/cm. To the best of our knowledge, complex 1 represents the first rhenium-based complex reported with ferroelectricity. [Copyright &y& Elsevier]

Three N,N-bidentate ligands, 5,5′-dibromo-2,2′-bipyridine (L1) and two carbazole containing ligands of 5-bromo-5′-carbazolyl-2,2′-bipyridine (L2), 5,5′-dicarbazolyl-2,2′-bipyridine (L3), and their corresponding rhenium Re(CO)3Cl(L) complexes (ReL1–ReL3) have been successfully synthesized and characterized by elemental analysis, 1H NMR and IR spectra. Their photophysical properties and thermal analysis, along with the X-ray crystal structure analysis of L3and complexes ReL1and ReL3are also described. In CH2Cl2solution at room temperature, all complexes display intense absorption bands at ca.220–350 nm, which can be assigned to spin-allowed intraligand (π→π*) transitions, and the low energy broad bands in the 360–480 nm region are attributed to the metal to ligand charge-transfer dπ(Re)→π* (diimine) (MLCT). The introduction of carbazole moieties improves the MLCT absorption and molar extinction coefficient of these complexes. Upon excitation at the peak maxima, all complexes show strong emissions around 620 nm, which are assigned to dπ(Re)→π* (diimine) MLCT phosphorescence. The photoluminescence lifetime decay of Re(I) complexes were measured and the quantum efficiencies of the rhenium(I) complexes were calculated by using air-equilibrated [Ru(bpy)3]2+·2Cl−aqueous solution as standard (Φstd= 0.028). The complexes with appended carbazole moieties exhibit enhanced luminescence performances relative to ReL1. [ABSTRACT FROM AUTHOR]