A series of 1,8-naphthyridine derivatives containing vinyl, 2-(2-acetylamino-pyridine-6-ethylene)-4-methyl-7-acetylamino-1,8-naphthy ridine (L-1), 2-(2-acetylamino-pyridine-6-ethylene)-1,8-naphthyridine (L-2), 2-(2-acetylamino-pyridinyl-6ethylene)-4-methyl-7-hydroxyl-1,8-naphthyrid ine (L-3), 2-(2-diacetylamino-pyridiny1-3-ethylene)-7-diacetylamino-1,8-naphthyridi ne (L-4), and 7-(2-diacetylamino-pyridiny1-3-ethylene)-4'-acetyl-pyrrolo[1',5'-a]-1,8-naphthyridine (L-5), as well as complexes [CuL1(PCy3)](BF4)(2) (1) (PCy3 = tricyclohexylphosphine), [Cu2L1(PPh3)(4)](BF4)(2) (2) (PPh3 = triphenylphosphine), [Cu2L1(dppm)](BF4)(2) (3) (dppm = bis(diphenylphosphino)methane), and [Cu-2(L-1)(dcpm)][BF4](2) (4) (dcpm = bis(dicyclohexylphosphino)methane, were synthesized. All these compounds, except for L-1 and L-2, were characterized by single crystal X-ray diffraction analysis, and a comprehensive study of their spectroscopic properties involving experimental theoretical studies is presented. We found an intramolecular 1,3-hydrogen transfer during the formation of L-3 and L-4, which in the case of the latter plays an important role in the 1,5-dipolar cyclization of L-5. The spectral changes that originate from an intramolecular charge transfer (ICT) in the form of a pi(py)->pi(napy)* transition can be tuned through acid/base-controlled switching for L-1-L-3. A photoinduced isomerization for L-1-L-3, 1, and 2 having flexible structures was observed under 365 nm light irradiation. Quantum chemical calculations revealed that the dinuclear complexes with structural asymmetry exhibit different metal-to-ligand charge-transfer transitions.