title: Probing the Protonation State and the Redox-Active Sites of Pendant Base Iron(II) and Zinc(II) Pyridinediimine Complexes.
abstract: Utilizing the pyridinediimine ligand [(2,6-(i)PrC6H3)N═CMe)(N((i)Pr)2C2H4)N═CMe)C5H3N] (didpa), the zinc(II) and iron(II) complexes Zn(didpa)Cl2 (1), Fe(didpa)Cl2 (2), [Zn(Hdidpa)Cl2][PF6] (3), [Fe(Hdidpa)Cl2][PF6] (4), Zn(didpa)Br2 (5), and [Zn(Hdidpa)Br2][PF6] (6), Fe(didpa)(CO)2 (7), and [Fe(Hdidpa)(CO)2][PF6] (8) were synthesized and characterized. These complexes allowed for the study of the secondary coordination sphere pendant base and the redox-activity of the didpa ligand scaffold. The protonated didpa ligand is capable of forming metal halogen hydrogen bonds (MHHBs) in complexes 3, 4, and 6. The solution behavior of the MHHBs was probed via pKa measurements and (1)H NMR titrations of 3 and 6 with solvents of varying H-bond accepting strength. The H-bond strength in 3 and 6 was calculated in silico to be 5.9 and 4.9 kcal/mol, respectively. The relationship between the protonation state and the ligand-based redox activity was probed utilizing 7 and 8, where the reduction potential of the didpa scaffold was found to shift by 105 mV upon protonation of the reduced ligand in Fe(didpa)(CO)2.
authors.forename: Mayra
authors.initials: M
authors.lastname: Delgado
authors.forename: Samantha K
authors.initials: SK
authors.lastname: Sommer
authors.forename: Seth P
authors.initials: SP
authors.lastname: Swanson
authors.forename: Robert F
authors.initials: RF
authors.lastname: Berger
authors.forename: Takele
authors.initials: T
authors.lastname: Seda
authors.affiliation: §Department of Chemistry, University of Oregon, Eugene, Oregon 97403, United States.
authors.forename: Lev N
authors.initials: LN
authors.lastname: Zakharov
authors.forename: John D
authors.initials: JD
authors.lastname: Gilbertson
mesh_terms: D006219:Halogens / Q000737:chemistry; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007097:Imines / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011522:Protons; D015032:Zinc / Q000737:chemistry*
chemical_list: D006219:Halogens; D007097:Imines; D008024:Ligands; D009942:Organometallic Compounds; D011522:Protons; D007501:Iron; D015032:Zinc