Synthesis, structures and spectroscopic properties of new 1,2-bis[2-(4-methyl-7-acetylamino-1,8-naphthyridine)]ethylene ligand and its binuclear copper(I) complexes

► 2-Bis[2-(4-methyl-7-acetylamino-1,8-naphthyridine)]ethylene is synthesized. ► Its binuclear copper(I) complexes with phosphine ligand are obtained. ► The complexes are structurally characterized through single crystal X-ray diffraction. ► Transient absorption and emission spectra of the compounds are also investigated.