Synthesis and characterization of ruthenium (II) tetraphenylporphyrin with redox active axial ligands for molecular wires

University of Minnesota M.S. thesis. May 2016. Major: Chemistry. Advisor: Victor Nemykin. 1 computer file (PDF); vii, 81 pages.Four new ruthenium(II) tetraphenylporphyrin with redox active axially coordinated ligands including two new heterotrinuclear Fe-Ru-Fe complexes of the ruthenium(II) tetraphenylporphyrin axially coordinated with a pair of isocyanoferrocene ((FcNC)2RuTPP) or 1,1'-diisocyanoferrocene (([C5H4NC]2Fe)2RuTPP) ligands [Fc = ferrocenyl, TPP = 5,10,15,20-tetraphenylporphyrinato(2-) anion], and two new isocyanoazulene containing complexes (2-CNAz)2RuTPP ( 2-CNAz = 2-isocyanoazulene) and (6-CNAz)2RuTPP ( 6-CNAz = 6-isocyanoazulene) were synthesized and characterized by UV-vis, MCD, NMR, and FTIR spectroscopies as well as by electrospray ionization mass spectrometry and single crystal X-ray diffraction. Isolation of insoluble polymeric {([C5H4NC]2Fe)RuTPP}n molecular wires was also achieved for the first time. The redox properties of the new trinuclear (FcNC)2RuTPP and ([C5H4NC]2Fe)2RuTPP complexes were probed using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation methods and correlated to those of the bis(tert-butylisocyano)ruthenium(II) tetraphenylporphyrin reference compound, (t-BuNC)2RuTPP, as well as (2-CNAz)2RuTPP and (6-CNAz)2RuTPP complexes. In all cases, the first oxidation process was attributed to the reversible oxidation of the RuII center. The second and third reversible oxidation processes in (FcNC)2RuTPP are separated by ~100 mV and were assigned to two single-electron FeII/FeIII couples suggesting a weak long-range iron-iron coupling in this complex. Electrochemical data acquired for ([C5H4NC]2Fe)2RuTPP complex are complicated by the interaction between the axial 1-1,1'-diisocyanoferrocene ligand and the electrode surface as well as by axial ligand dissociation in solution. Spectroelectrochemical and chemical oxidation methods were used to elucidate spectroscopic signatures of the [(RCN)2RuTPP]n+ species in solution. In both (2-CNAz)2RuTPP and (6-CNAz)2RuTPP complexes, the first oxidation process was attributed to the reversible oxidation of RuII center and the second oxidation process was assigned to the reversible oxidation of porphyrin core. The third and fourth irreversible processes were assigned to the oxidation of two isocyanoazulene axially coordinated ligands. DFT and TDDFT calculations aided in correlating spectroscopic and redox properties of complexes with their electronic structures