The binuclear dual emitter [Br(CO)3Re(P⋯⋯N)(N⋯⋯P)Re(CO)3Br] (P⋯⋯N): 3-chloro-6-(4- diphenylphosphinyl)butoxypyridazine, a new bridging P,N-bidentate ligand resulting from the ring opening of tetrahydrofuran