Luminescence properties and DFT calculations of lanthanide(III) complexes (Ln = La, Nd, Sm, Eu, Gd, Tb, Dy) with 2,6-bis(5-methyl-benzimidazol-2-yl)pyridine

Seven new complexes obtained of hydrated lanthanide(III) nitrates with 2,6-bis(5-methyl-benzimidazol-2-yl)pyridine (bmbp) having the formula [LnIII(bmbp)(NO3)2]NO3 n-H2O (where LnIII = LaIII, NdIII, SmIII, EuIII, GdIII, TbIII, DyIII) have been prepared and characterized by ultraviolet–visible and infrared absorption spectroscopies, molar conductivity and elemental composition. The emission spectra of the all complexes have also been analyzed; it has been detected that all complexes revealed the luminescence of bmbp. Samarium and europium complexes also displayed the corresponding lanthanides luminescence. The metal ion is coordinated to seven atoms resultant to three nitrogens of bmbp and to two oxygens for each of the bidentate nitrate groups. Density functional theory calculations were utilized to designate the singlet and triplet excited state energy levels of bmbp.