FeL(CO) and [FeL(NO)]+ (H2L = meso-[o-(4-dimethylamino)butyramidophenyl]triphenylporphyrin) were prepared and studied by UV, MCD, EPR, and cyclic voltammetry. The reaction equilibrium constant (1.38 ?107 M-1) of FeL with CO was measured. The 5th ligand affects the equilibrium constant The tailed Fe(II) porphyrin complex is coordinated by NO in the 6th coordination position; the axial coordinated base (tail) is away from Fe because the unpaired electrons of NO has to go into the antibonding orbital of sp3(N) + dz2(Fe). The redox of CO, NO complexes is irreversible and suggests the electrode reaction involving an electron mechanism.

Key words: ULTRAVIOLET SPECTROPHOTOMETRY, CARBON MONOXIDE, MOLECULAR STRUCTURE, IRON COMPLEX, SPECTROGRAPHIC ANALYSIS, EQUILIBRIUM CONSTANT, MOLECULAR ORBITAL THEORY, DIMETHYLAMINO, DIATOMIC MOLECULE, ELECTROCHEMISTRY