As a continuation of our previous investigations aimed at the synthesis of novel nitrogen-containing heterocycles and their metal complexes, we have now prepared two series of compounds incorporating a phthalazine ring at the position C
2 of 4,5-dihydro-1
H-imidazole. The starting phthalazine (
I) in the reaction with 2-chloroimidazoline (
II) gives rise to the formation of pseudobase
III. Then, compound
III upon treatment with HOSA yields betaine which under basic conditions gives 2-(4,5-dihydro-1
H-imidazol-2-yl)phthalazin-1(2
H)-imine (
IV). In turn, the reactions of compound
IV with a variety of acyl and sulfonyl chlorides lead to the formation of benzamides (
V) and benzenesulfonamides (
VI). Moreover, compounds
V and
VI can be transformed into corresponding 2-(4,5-dihydro-1
H-imidazol-2-yl)phthalazin-1(2
H)-one derivatives
VII and
VIII. Such ligands are susceptible to the reaction with CuCl
2 giving rise to the formation of corresponding copper(II) complexes: dichloro[2-(4,5-dihydro-1
H-imidazol-2-yl)phthalazin-1(2
H)-imine]copper(II) (
1), dichloro[2-(1-benzoyl-4,5-dihydro-1
H-imidazol-2-yl)phthalazin-1(2
H)-one]copper(II) (
2) and dichloro{bis-[2-(1-(phenylsulfonyl)-4,5-dihydro-1
H-imidazol-2-yl)phthalazin-1(2
H)-one]}copper(II) (
3). The most promising results of biological studies were obtained for complex
1 towards the HeLa cell line (IC
50 = 2.13 μM) without a toxic effect against fibroblasts BALB/3T3 (IC
50 = 135.30 μM), which pointed towards its selectivity as a potential antitumor agent. It should be pointed out, that corresponding free ligand 2-(4,5-dihydro-1
H-imidazol-2-yl)phthalazin-1(2
H)-imine (
IV) was less active than its metal complex (IC
50 = 87.74 μM).
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