Synthesis and Characterization of Aryl Acylguanidines and Their Copper(Ⅱ) Complexes

A series of eight N-mono-substituted aryl acylguanidines L1~8 were synthesized from the reactions of their parent acylthioureas and respective primary amines, including five R1C(O)N=C(NHR2)2 with balanced arms(denoted as R1–R2–R2: Ph–Ar’–Ar’, L1(1);Ph–Ar’’–Ar’’, L2(2);1-Naph–Ar’–Ar’, L3(3);1-Naph–Ar’’–Ar’’, L4(4);2-Naph–Ar’’–Ar’’, L[5(5);Ar’ = 2,6-Me2C6H3, Ar’’ = 2,6-iPr2C6H3) and three R1C(O)N=C(NHR2)NHR3 with unbalanced arms(denoted as R1–R2–R3: Ph–Ar’–Ph, L6(6);Ph–Ar’ –Ph, L7(7);Ph–Ar’ –Ar’, L8(8)). Treatment of L1~5(1~5) with copper acetate in a molar ratio of 2:1 in dichloromethane led to the formation of homoleptic Cu(Ⅱ) complexes trans-L2n’Cu(9~13), in which the Cu(Ⅱ) center was stabilized by deprotonated ligands Ln’(n = 1~5) in the O,N-bidentate mode. When similar reactions of L6(Ph–Ar’–Ph)(6) and L7(Ph–Ar’’–Ph)(7) that contain unbalanced arms were investigated, the Cu(Ⅱ) products trans-L26’Cu(14) and trans-L27’Cu(15) were formed by deprotonating the bulky amine groups in Ln(-NHAr’ for L6 and-NHAr’’ for L7) rather than the-NHPh group. In sharp contrast, trans-L28’Cu(16) was obtained from two-arm unbalanced L8(Ph–Ar’’–Ar’)(8) not by deprotonating the more bulky-NHAr’’ group but the relatively less bulky-NHAr’ group. In a further exploration, the reaction of 1:1 mixed ligands Ln and Lm with copper acetate was found to give only homoleptic Cu(Ⅱ) complex L2n’Cu instead of the heteroleptic one Ln’CuLm’. The in vitro antibacterial activity of Ln was evaluated against S. aureus, E. coli and C. albicans by determining the minimum inhibitory concentrations(MICs) using Kirby-Bauer test.