01939nas a2200181   4500008004100000022001400041245010000055210006900155260007100224300001600295490000800311520123300319100001901552700001601571700001701587700002401604856012901628       2015                        eng d  a1520-610600aHydrogen bond and ligand dissociation dynamics in fluoride sensing of Re(I)-polypyridyl complex0 aHydrogen bond and ligand dissociation dynamics in fluoride sensi  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcNOV  a14952-149580 v1193 a<p>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)(3)Cl(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 H-1 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 [ReII(bpy(center dot-)-phenolate(-))(CO)(3)Cl]* undergoes CO dissociation in the ultrafast time scale of similar to 3 ps. A concerted mechanism of hydrogen cleavage and coordination change is established in anion sensing studies of the rhenium complex.</p>1 aVerma, Sandeep1 aAute, Sunil1 aDas, Amitava1 aGhosh, Hirendra, N.  uhttps://library.ncl.res.in/content/hydrogen-bond-and-ligand-dissociation-dynamics-fluoride-sensing-rei-polypyridyl-complex-103024nas a2200193   4500008004100000022001400041245017500055210006900230260000900299300001400308490000700322520228300329100001602612700001802628700001602646700001702662700002402679856012702703       2019                        eng d  a1474-905X00aHydrogen bond assisted photoinduced intramolecular electron transfer and proton coupled electron transfer in an ultrafast time domain using a ruthenium-anthraquinone dyad0 aHydrogen bond assisted photoinduced intramolecular electron tran  cOCT   a2430-24410 v183 a<p>Quinones play a significant role as primary electron acceptors in the natural photosynthetic system of photosystem II, and their reduction is known to be facilitated by hydrogen-bond donors or protonation. In this study, a ruthenium(ii) polypyridyl complex 1 coupled to an anthraquinone (AQ) functionality through a rigid imidazole (Im) spacer has been synthesized to examine the effect of H-bonding on both the thermal and photoinduced electron transfer reactions. The anthraquinone moiety of complex 1 is fused to a benzi-imidazole system bearing C &amp; xe001;(OMIDLINE)-M-AQ HORIZONTAL ELLIPSISHNIm based H-bonding at one side of the anthraquinone moiety so that intramolecular hydrogen bonding from the imidazole group to the nearby quinone carbonyl can occur. The hydrogen bond formation involving the semiquinone radical anion produced through the photoinduced reduction process in Ru-im-AQ and the imidazole proton in complex 1 resulted in a significant positive shift of one electron reduction potential of complex 1. The kinetics for the formation of the charge-separated states was explored by using femtosecond transient absorption spectroscopy. Hydrogen bonding between water and the reduced anthraquinone accounted for thermodynamic and kinetic stabilization of these charge-separated states. An attempt has been made to assess the relative importance of the driving force and solvent polarity, in the rates of photoinduced electron transfer in complex 1. The 490 nm transient absorption band of anthraquinone radical anions (AQ(-)) and a broad absorption in the 580-750 nm region having maxima at similar to 690 nm have been observed and this is attributed to the generation of a transient Ru3+-species of the corresponding complex 1. Addition of water entails an acceleration of electron transfer rates by a factor of 3.33. The system investigated may serve as a model for the mechanistic diversity of PCET reactions in general with water as a primary proton donor. Furthermore, our studies are relevant for understanding proton-coupled electron transfer (PCET) reactivity of electronically excited states at a fundamental level because changes in hydrogen-bonding strength accompanying changes in redox states may be regarded as a variant form of PCET.</p>
1 aDey, Ananta1 aDana, Jayanta1 aAute, Sunil1 aDas, Amitava1 aGhosh, Hirendra, N.  uhttps://library.ncl.res.in/content/hydrogen-bond-assisted-photoinduced-intramolecular-electron-transfer-and-proton-coupled