Syntheses, electrolytic behaviour and antifungal activities of Zn(II) complexes of isomers of 3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L). Crystal and molecular structure of [ZnLB(NO3)]NO3 (LB = a,e,a,e-L)

The isomeric cyclam ligands Me8[14]anes, designated by LA, LB and LC, produce, on reaction with zinc(II)nitrate, zinc(II)sulphate or zinc(II)chloride corresponding complexes, i.e. dinitrato/mononitrato-nitrate complexes [ZnL(NO3)2]/[ZnL(NO3)](NO3) (L = LA, LB or LC, where the indices A, B and C refer to differing orientations of the four methyl groups on secondary carbons of Me8[14]ane), the diaqua-sulphates [ZnL(H2O)2]SO4 (L = LA, LB or LC), and the diaqua dichloride and dichlorido complexes [ZnL(H2O)2]Cl2 (L = LA or LC) or [ZnLBCl2], respectively. The complexes have been characterised on the basis of elemental analyses, IR, UV–Vis, 1H and 13C NMR spectroscopies, magnetic and conductance data. The structure of [ZnLB(NO3)](NO3) has been determined by X-ray crystallography. The zinc centre is coordinated to a N4O donor set in a square-pyramidal geometry. The complexes show differing electrolytic behaviour in different solvents. In chloroform, the complexes are non-electrolytes, indicating that both anions are coordinated to Zn2+. Antifungal activity of the ligands and complexes against the phytopathogenic fungi Alternaria alternata and Colletotrichum corcolei have been investigated, and positive results were noted.

Graphical abstractA series of zinc(II) compounds of three isomers of an octamethyl substituted tetraaza-macrocyclic ligand were thoroughly characterised. Some of them exhibited different electrolytic behaviour in different solvents. Some examples demonstrated significant antifungal activity.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The cyclam ligands Me8[14]ane (LA, LB and LC) undergo complexation with Zn2+. ► The structure of [ZnLB(NO3)]NO3 has been confirmed by X-ray crystallography. ► Some complexes show differing electrolytic behaviour in different solvents. ► Studies on the activity against phytopathogenic fungi exhibit positive results.