Composition of biligand compounds Cu(C 3 H 4 N 2 , C 4 H 6 N 2 ) x ( ) 2 • nH 2 O obtained by reaction of aqueous suspensions of prepared poorly soluble copper(II) benzoate Cu(C 7 H 5 O 2 ) 2 • 3H 2 O and nicotinate Cu(C 6 H 4 NO 2 ) 2 • H 2 O with imidazole and 2-methylimidazole has been determined. Mono-and biligand salts have been analyzed and their thermal decomposition has been studied. IR spectroscopy has shown the participation of pyridine nitrogen of imidazole and carboxylic groups of aromatic acids in binding to copper(II) ion. Composition and stability of copper(II) benzoate complex, solubility constant for salt Cu(C 7 H 5 O 2 ) 2 • 3H 2 O at ionic strength I = 0.1 have been determined by solubility method, pH potentiometry, and photometry. Co-crystals/salts of composition C 3 H 4 N 2 • C 7 H 6 O 2 (pH 8.0), C 3 H 4 N 2 • C 6 H 5 NO 2 (pH 7.4) and 3(C 4 H 6 N 2 ) • C 19 H 19 O 6 N 7 • 2H 2 O (pH ~7) have been prepared and studied by thermogravimetric analysis. X-ray powder diffractograms have been recorded for initial compounds and their reaction products (imidazole-benzoic acid, 2-methylimidazole-folic acid systems).