Abstract

The reaction of [(ReBr)-Br-I(CO)(3)(THF)](2) with phenanthroline in solution leads to the diimine rhenium(I)tricarbonyl Rphen)Re(CO)(3)Br] and the dimer [(CO)(3)(phen)Re(mu-OH)(phen)Re(CO)(3)]Br-+(-)(1(+)Br(-)) as a by-product (similar to 5% yield). This latter bimetallic compound crystallizes as a mixture of three polymorphs, with variable amount of solvent: 1(+)Br(-)center dot CHCl3 (triclinic and orthorhombic) and 1(+)Br(-)center dot 2(CHCl3) (triclinic). Rietveld analysis showed 38, 54 and 8% of 1(+)Br(-)center dot CHCl3 (triclinic), 1(+)Br(-)CHCl(3) (orthorhombic) and 1(+)Br(-)center dot 2(CHCl3) (triclinic) respectively. The 1(+) cation shows two [Re-I(phen)(CO)(3)](+) units connected by means of a central hydroxyl group. Noteworthy, the bridging Re-O-Re angle varies between 130.9(7)degrees to 140.7(2)degrees along the polymorphic series. UV-Vis spectrum for the 1(+) shows a broad absorption band around 390 nm in CH2Cl2 which has been attributed to has MLCT character (Re(d(pi)) -> pi*(phen)) as confirmed by DFT. Excitation at 405 nm in solution leads to emission at 595 nm (DCM), 605 nm (DMF) and 625 nm (CH3CN). The emission follows a mono-exponential law of decay and has lifetime of 405.8 ns (DCM). The solid-state polymorphic mixture absorbs around 460 nm. Excitation of the solid at 320 nm leads to emission with a maximum at 575 nm, which follow a bi-exponential law of decay with two components, a short one tau(1) of 27.0 ns and longer one tau(2) of 178.5 ns. These results suggest that the emitting state does not vary as function of the molecular geometry. (C) 2019 Elsevier Ltd. All rights reserved.