Do the bridging angle affect the luminescent properties of [(CO)3(phen)Re(µ-OH)Re(phen)(CO)3]+?. An experimental and computational study on three polymorphs

C. Muñoz (1) , M. Saldías (1) , P. Oyarzún (1) , J.-Y. Saillard (2) , J.-R. Hamon (2) , G. Calvez (2) , N. Pizarro (1) , A. Vega (1)

1 UNAB - Universidad Andrés Bello [Santiago]
2 ISCR - Institut des Sciences Chimiques de Rennes

The reaction of [ReIBr(CO)3(THF)]2 with phenanthroline in solution leads to the diimine rhenium(I)tricarbonyl [(phen)Re(CO)3Br] and the dimer [(CO)3(phen)Re(µ-OH)(phen)Re(CO)3]+Br− (1+Br−) as a by-product (~5% yield). This latter bimetallic compound crystallizes as a mixture of three polymorphs, with variable amount of solvent 1+Br−·CHCl3 (triclinic and orthorhombic) and 1+Br−·2(CHCl3) (triclinic). Rietveld analysis showed 38, 54 and 8% of 1+Br−·CHCl3 (triclinic), 1+Br−·CHCl3 (orthorhombic) and 1+Br−·2(CHCl3) (triclinic) respectively. The 1+ cation shows two [ReI(phen)(CO)3]+ units connected by means of a central hydroxyl group. Noteworthy, the bridging Re–O–Re angle varies between 130.9(7)° to 140.7(2)° 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(dπ) → π*(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 τ1 of 27.0 ns and longer one τ2 of 178.5 ns. These results suggest that the emitting state does not vary as function of the molecular geometry.

Mots clés: Rhenium; Bridging angle; Density functional calculations; Luminescence; Polymorphism

Domaines: Chimie de coordination; Chimie théorique et/ou physique

C. Muñoz, M. Saldías, P. Oyarzún, J.-Y. Saillard, J.-R. Hamon, et al.. Do the bridging angle affect the luminescent properties of [(CO)3(phen)Re(µ-OH)Re(phen)(CO)3]+?. An experimental and computational study on three polymorphs. Polyhedron, 2019, 173, pp.114150. ⟨10.1016/j.poly.2019.114150⟩. ⟨hal-02367954⟩