Modulation of trans-to-cis photoisomerization and photoluminescence of 1,2-bis(4-pyridyl)ethylene or 4-styrylpyridine coordinated to fac-tricarbonyl(5-chloro-1,10-phenathroline)rhenium(I)

► fac-[Re(CO)3(Clphen)(trans-L)]+ Complexes were synthesized and characterized. ► The photoisomerization quantum yields (Φ) were accurately determined by 1H NMR spectroscopy. ► Their Φ were compared with analogous Re-complexes: fac-[Re(CO)3(NN)(trans-L)]+, NN = phen and ph2phen. ► Φ Decreased as the 3ILtrans-L and 3MLCTRe→NN excited states become closer. ► The behavior was discussed in terms of the excited state energy gaps.