title: Modulation of Axial-Ligand Binding and Releasing Processes onto the Triazole-Bearing Nickel(II) Picket-Fence Porphyrins: Steric Repulsion versus Hydrogen-Bonding Effects.
abstract: N-(p-Methoxycarbonylbenzyl) triazole (BTz) substituents have been introduced to Ni(II) porphyrins (NiPs), in which their modulated axial-coordination processes have been investigated. For this study, the two types of ligands, neutral pyridine versus anionic cyanide, were employed to investigate an effect of BTz substituents. The unique microenvironments given by the BTz substituents provided two different effects on the axial-coordination processes of NiPs on the ground and excited states: (1) steric shielding and (2) donation of hydrogen-bonding sites. The steric shielding diminished the binding affinity of pyridine, while the cooperation of hydrogen bonds extraordinarily strengthened the binding affinity of CN(-). Interestingly, it was observed that the binding of CN(-) with the supporting of BTz substituents accompanied nonplanar distortion of NiPs. Such conformational change perturbed the electronic structure of NiPs, which gave rise to the modulation of coordination processes of NiPs in the excited state. As a consequence, photoinudced ligand binding and releasing processes of four- and six-coordinated NiPs were changed into the dominant photoinduced ligand releasing process.
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Juwon
authors.initials: J
authors.lastname: Oh
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Hongsik
authors.initials: H
authors.lastname: Yoon
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Young Mo
authors.initials: YM
authors.lastname: Sung
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Philjae
authors.initials: P
authors.lastname: Kang
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Moon-Gun
authors.initials: MG
authors.lastname: Choi
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Woo-Dong
authors.initials: WD
authors.lastname: Jang
authors.affiliation: †Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, ‡Biopolymer Laboratory and Department of Chemistry, and §Molecular Structure Laboratory and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
mesh_terms: D003486:Cyanides / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D055668:Photochemical Processes; D011166:Porphyrins / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013057:Spectrum Analysis; D014230:Triazoles / Q000737:chemistry*
chemical_list: D003486:Cyanides; D011166:Porphyrins; D011725:Pyridines; D014230:Triazoles; D009532:Nickel; C023666:pyridine