In　this　paper,　a　series　of　mononuclear/binuclear　Cu(i)　complexes,　[Cu-I(dpq)(PPh3)(2)](CF3SO3)center　dot　CH3OH　(1a),　[Cu-I(dppz)(PPh3)(2)](CF3SO3)center　dot　CH3OH　(1b),　[Cu-2(I)(dpq)(2)(dppm)(2)](CF3SO3)(2)　(2a),　[Cu-2(I)(dppz)(2)(dppm)(2)](CF3SO3)(2)　(2b),　[Cu-I(dpq)(dppp)](CF3SO3)center　dot　CH3OH　(3a),　[Cu-I(dppz)(dppp)](CF3SO3)center　dot　CH3OH　(3b),　[Cu-I(dpq)(POP)](CF3SO3)center　dot　CH3OH　(4a),　[Cu-I(dppz)(POP)](CF3SO3)center　dot　CH3OH　(4b),　[Cu-I(dpq)(xantphos)](CF3SO3)　(5a),　and　[Cu-I(dppz)(xantphos)](CF3SO3)　(5b)　{dppm　=　1,1-bis(diphenylphosphino)methane;　dppp　=　1,3-bis(diphenylphosphino)propane;　POP　=　bis[2-(diphenylphosphino)phenyl]ether;　xantphos　=　4,5-bis(diphenylphosphino)-9,9-dimethylxanthene;　dpq　=　pyrazino[2,3-f][1,10]-phenanthroline;　dppz　=　dipyrido[3,2-a:　2　＇,3　＇-c]phenazine}　have　been　synthesized　and　characterized　by　using　IR,　NMR,　elemental　analysis,　terahertz　(THz)　time-domain　absorption　spectroscopy,　UV-vis　and　fluorescence　spectroscopy　methods　as　well　as　single　crystal　X-ray　diffraction　analysis.　The　single　crystal　X-ray　diffraction　results　indicated　that　the　immediate　geometry　around　each　central　Cu(i)　in　the　above　complexes　is　a　distorted　tetrahedron　with　the　central　metal　atom　being　coordinated　by　the　two　phosphorus　atoms　of　the　phosphine　ligands　and　two　nitrogen　atoms　of　the　bidentate　N-containing　heterocyclic　ligand　moieties.　It　is　found　that　complexes　1a-5a　and　5b　show　photoluminescence　in　the　solid　state　at　room　temperature　with　the　highest　quantum　yield　up　to　0.5519,　and　the　increased　conjugation　in　the　diimine　ligands　leads　to　emission　reduction　along　with　a　red-shift　in　the　emission　maxima.　Detailed　photo-physical　studies　and　density　functional　theory　calculations　(DFT)　of　these　complexes　have　revealed　that　their　lowest　energy　absorptions　and　emissions　are　ascribed　to　metal-to-ligand　charge　transfer　(MLCT)　excited　states.　The　above　results　indicate　that　conjugation　effects　of　N-heteroaromatic　ligands　play　a　significant　role　in　the　emission　properties　of　mononuclear/binuclear　Cu(i)　complexes.　For　the　first　time,　terahertz　time-domain　spectroscopy　is　applied　for　qualitatively　understanding　the　photophysical　properties　of　complexes,　revealing　that　terahertz　time-domain　spectra　are　sensitive　to　the　weak　interaction　between　the　ligands,　especially　the　diimine　ligands,　and　terahertz　spectra　are　strongly　correlated　with　photoluminescence　quantum　yields　of　the　complexes.