title: Hydrogen Bond and Ligand Dissociation Dynamics in Fluoride Sensing of Re(I)-Polypyridyl Complex.
abstract: Hydrogen bonding interaction plays an essential role in the early phases of molecular recognition and colorimetric sensing of various anions in aprotic media. In this work, the host-guest interaction between fac-[Re(CO)3Cl(L)] with L = 4-([2,2'-bipyridin]-4-yl)phenol and fluoride ions is investigated for the hydrogen bond dynamics and the changing local coordination environment. The stoichiometric studies using (1)H NMR and ESI-MS spectroscopies have shown that proton transfer in the H-bonded phenol-fluoride complex activates the dissociation of the CO ligand in the Re(I) center. The phenol-to-phenolate conversion during formation of HF2(-) ion induces nucleophilic lability of the CO ligand which is probed by intraligand charge transfer (ILCT) and ligand-to-metal charge transfer (LMCT) transitions in transient absorption spectroscopy. After photoexcitation, phenol-phenoxide conversion rapidly equilibrates in 280 fs time scale and the ensuing excited state [Re(II)(bpy•(-)-phenolate¯) (CO)3Cl]* undergoes CO dissociation in the ultrafast time scale of ∼3 ps. A concerted mechanism of hydrogen cleavage and coordination change is established in anion sensing studies of the rhenium complex.
authors.affiliation: Radiation and Photochemistry Division, Bhabha Atomic Research Centre , Mumbai, 400085, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Verma
authors.affiliation: CSIR-National Chemical Laboratory, Pune, 411008, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Aute
authors.affiliation: CSIR-National Chemical Laboratory, Pune, 411008, India.
authors.forename: Amitava
authors.initials: A
authors.lastname: Das
authors.affiliation: Radiation and Photochemistry Division, Bhabha Atomic Research Centre , Mumbai, 400085, India.
authors.forename: Hirendra N
authors.initials: HN
authors.lastname: Ghosh