By using two potential tridentate ligands, HL1 [4- chloro-2-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol] and HL2 [4-chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phenol], which differ by one methylene group in the alkyl chain, four new ZnII complexes, namely, [Zn(L2H)2](ClO4)2 (1), [Zn(L1)(H2O)2][Zn(L1)(SCN)2] (2), [Zn(L1)(dca)]n (3), and [Zn2(L1)2(N3)2(H2O)2] (4) [where dca = dicyanamide anion] were synthesized and structurally characterized. The results indicate that the slight structural difference between the ligands, HL1 and HL2, because of the one methylene group connecting the nitrogen atoms provokes a chemical behavior completely different from what was expected. Any attempt to isolate the Zn(L2) complexes with thiocyanato, dicyanamido, and azide was unsuccessful, and perchlorate complex 1 was always obtained.