A new series of lanthanide(III) nitrate complexes with 10-(2-dimethylamino-1-methyl) phenothiazine (isopromethazine) having the general formula [Ln(IP)₂(NO₃)₂]NO₃, where Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and IP=isopromethazine have been prepared and characterized by elemental analysis, molar conductance, electronic, infrared, proton NMR spectra, magnetic moments and thermogravimetric studies. Isopromethazine acts as a bidentate ligand, coordinating through heterocyclic nitrogen and tertiary alkyl side chain nitrogen atoms. Two of the nitrate groups are coordinated in a bidentate fashion to the metal ion, while another nitrate ion remains uncoordinated. A coordination number of eight may be assigned to the metal ion in these complexes. The electronic spectra reveal the weak covalent character of the metal-ligand bond.

Six new dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines having the general formula M₂O₄(L)₂(H₂O)₂ [where M = molybdenum or tungsten and L = N-alkylphenothiazines] have been synthesised. The complexes have been characterised on the basis of analytical, molar conductance, magnetic susceptibility, spectral data, TGA and DTA. The low magnetic moments for the complexes are due to spin-spin interaction or metal-metal bonding. The interactions of these complexes with some biologically important amino acids have been studied.