Structural and NMR Spectroscopic Investigations of CuI, CuII, NiII, ZnII and FeII Complexes of 2, 9‐Di‐(Benzothiazolino)‐1,10‐Phenanthroline

Synthesis and characterisation of a disubstituted phenanthroline, “dbt‐phen” (“dbt‐phen”, 2,9‐di(benzothiazolino)‐1,10‐phenanthroline) 1 and its CuI, CuII, NiII, ZnII and FeII complexes are reported. Three different coordination modes of the ligand viz., bis(didentate), tridentate and tetradentate are observed. Under various experimental conditions, 1 forms a double‐stranded dicopper(I)helicate, [CuI2(dbt‐phen)2]2+ 2; a mono(dbt‐phen) copper(II) complex, [CuII(dbt‐phen)(H2O)2]2+ 3, a NiII complex [Ni(dbt‐ phen)(NCMe)2(OH2)]2+ 4, a bis(dbt‐phen) zinc(II) complex, [ZnII(dbt‐phen)2]2+ 5 and a pseudo‐octahedral complex [FeII(dbt‐phen)Br2] 6. Crystal packing feature of the dicopper helicate [CuI(dbt‐phen)]2[BF4]2, 2+[BF4]2 reveals novel short contacts between BF4− ions and the hydrogens of the phenyl rings leading to the peculiar double stranded and helical topology. The complex [CuII(dbt‐phen)(OH2)2(ClO4)][ClO4], 3+[ClO4] exhibits both intra‐ and inter‐molecular H‐bonding interactions. 1H NMR spectral features of the ligand, copper(I) and zinc(II) complexes indicate that the free ligand and the copper(I) complex retain their solid state structures whereas the zinc(II) complex undergoes structural changes in solution. A disubstituted phenanthroline, dbt‐phen functions as bis‐didentate or tridentate or tetradentate forming helical or octahedral CuI, CuII, NiII, ZnII and FeII complexes of M2L2 or ML2 or ML stoichiometries. The 1H NMR spectral investigation indicates that dbt‐phen and dicopper(I) helicate retain their solid state structures in solution whereas the zinc(II) complex undergoes structural changes in solution.