The reactions of [Cu(CH3CN)(4)]ClO4 and 2-(diphenylphosphino)pyridine (dppy) with different halogen reagents NH4X (X = Cl-, Br- and l(-)) and four luminescent di-copper(i) coordination compounds, namely [Cu-2(mu-dppy)(3)Cl]ClO4 center dot H2O (1a), [Cu-2(mu-dppy)(3)Br]ClO4 (2a), Cu-2(mu-Br)(2)(mu-dppy)(eta-dppy)(2) (2b) and [Cu-2(mu-l)(2)(mu-dppy)(eta-dppy)(2)] (3b), were isolated. Intriguingly, X-ray crystallographic studies reveal that there were two kinds of Cue-core structural configuration induced by the differently sized halogen anions. With Cl--acting as a co-ligand, 1a featured a trefo...