A synthetic, structural, spectroscopic and DFT study of Re(I), Cu(I), Ru(II) and Ir(III) complexes containing functionalised dipyrido[3,2-a:2',3'-c]phenazine (dppz)

The ligands 11-cyanodipyrido[3,2-a:2',3'-c]phenazine and 2-(11-dipyrido[3,2-a:2',3'-c]phenazine)-5-phenyl-1,3,4-oxadiazole have been coordinated to Re(I), Cu(I), Ru(II) and Ir(III) metal centres. Single-crystal X-ray analyses were performed on fac-chlorotricarbonyl(11-cyanodipyrido[3,2-a:2',3'-c]phenazine)rhenium (C(22)H(9)ClN(5)O(3)Re, a=6.509(5), b=12.403(5), c=13.907(5) A, alpha=96.88(5), beta=92.41(5), gamma=92.13(5) degrees , triclinic, P1, Z=2) and bis-2,2'-bipyridyl(2-(11-dipyrido[3,2-a:2',3'-c]phenazine)-5-phenyl-1,3,4-oxadiazole)ruthenium triflate2 CH(3)CN (C(52)H(36)F(6)N(12)O(8)RuS(2), a=10.601(5), b=12.420(5), c=20.066(5) A, alpha=92.846(5), beta=96.493(5), gamma=103.720(5) degrees , triclinic, P1, Z=2). The ground- and excited-state properties of the ligands and complexes have been investigated with a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited-state lifetime studies. Spectroscopic, time-resolved and DFT studies reveal that the ligand-centred (LC) transitions and their resultant excited states play an important role in the photophysical properties of the complexes. Evidence for the presence of lower-lying metal-to-ligand charge-transfer transitions is obtained from resonance Raman spectroscopy, but nanosecond transient Raman experiments suggest that once excited, the (3)LC state is populated.