01768nas a2200169   4500008004100000245008600041210006900127260000800196300001600204490000700220520117600227100001901403700001801422700001701440700002601457856011501483       2011                        eng d00aExciton-coupled charge-transfer dynamics in a porphyrin J-aggregate/TiO 2 complex0 aExcitoncoupled chargetransfer dynamics in a porphyrin Jaggregate  cMAR  a3458–34640 v173 a<p>Exciton-coupled charge-transfer (CT) dynamics in TiO2 nanoparticles (NP) sensitized with porphyrin J-aggregates has been studied by femtosecond time-resolved transient absorption spectroscopy. J-aggregates of 5,10,15-triphenyl-20-(3,4-dihydroxyphenyl) porphyrin (TPPcat) form CT complexes on TiO2 NP surfaces. Catechol-mediated strong CT coupling between J-aggregate and TiO2 NP facilitates interfacial exciton dissociation for electron injection into the conduction band of the TiO2 nanoparticle in pulse width limited time (&lt;80 fs). Here, the electron-transfer (&lt;80 fs) process dominates over the intrinsic exciton-relaxation process (J-aggregates: ca. 200 fs) on account of exciton-coupled CT interaction. The parent hole on J-aggregates is delocalized through J-aggregate excitonic coherence. As a result, holes immobilized on J-aggregates are spatially less accessible to electrons injected into TiO2, and thus the back electron transfer (BET) process is slower than that of the monomer/TiO2 system. The J-aggregate/porphyrin system shows exciton spectral and temporal properties for better charge separation in strongly coupled composite systems.</p>1 aVerma, Sandeep1 aGhosh, Amrita1 aDas, Amitava1 aGhosh, Hirendra, Nath  uhttps://library.ncl.res.in/content/exciton-coupled-charge-transfer-dynamics-porphyrin-j-aggregatetio-2-complex02533nas a2200169   4500008004100000245015500041210006900196260000800265300001400273490000700287520185900294100001902153700001902172700001702191700002602208856012902234       2011                        eng d00aPhotophysical properties of ligand localized excited state in ruthenium(ii) polypyridyl complexes: a combined effect of electron donor-acceptor ligand0 aPhotophysical properties of ligand localized excited state in ru  cAUG  a9765-97730 v403 a<p>We have synthesized ruthenium(II) polypyridyl complexes (1) Ru(II)(bpy)2(L1), (2) Ru(II)(bpy)2(L2) and (3) Ru(II)(bpy)(L1)(L2), where bpy = 2,2′-bipyridyl, L1 = 4-[2-(4′-methyl-2,2′-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) and L2 = 4-(N,N-dimethylamino-phenyl)-(2,2′-bipyridine) and investigated the intra-ligand charge transfer (ILCT) and ligand–ligand charge transfer (LLCT) states by optical absorption and emission studies. Our studies show that the presence of electron donating –NMe2 functionality in L2 and electron withdrawing catechol fragment in L1 ligands of complex 3 introduces low energy LLCT excited states to aboriginal MLCT states. The superimposed LLCT and MLCT state produces redshift and broadening in the optical absorption spectra of complex 3 in comparison to complexes 1 and 2. The emission quantum yield of complex 3 is observed to be extremely low in comparison to that of complex 1 and 2 at room temperature. This is attributed to quenching of the 3MLCT state by the low-emissive 3LLCT state. The emission due to ligand localized CT state (ILCT and LLCT) of complexes 2 and 3 is revealed at 77 K in the form of a new luminescence band which appeared in the 670–760 nm region. The LLCT excited state of complex 3 is populated either via direct photoexcitation in the LLCT absorption band (350–700 nm) or through internal conversion from the photoexcited 3MLCT (400–600 nm) states. The internal conversion rate is determined by quenching of the 3MLCT state in a time resolved emission study. The internal conversion to LLCT and ILCT excited states are observed to be as fast as ∼200 ps and ∼700 ps for complexes 3 and 2, respectively. The present study illustrates the photophysical property of the ligand localized excited state of newly synthesized heteroleptic ruthenium(II) polypyridyl complexes.</p>1 aVerma, Sandeep1 aKar, Prasenjit1 aDas, Amitava1 aGhosh, Hirendra, Nath  uhttps://library.ncl.res.in/content/photophysical-properties-ligand-localized-excited-state-rutheniumii-polypyridyl-complexes02251nas a2200205   4500008004100000245015200041210006900193260000800262300001400270490000700284520148800291100001901779700002101798700001901819700001401838700001701852700002301869700002401892856012901916       2012                        eng d00aPhotosensitization of nanoparticulate TiO2 using a Re(I)-polypyridyl complex: studies on interfacial electron transfer in the ultrafast time domain0 aPhotosensitization of nanoparticulate TiO2 using a ReIpolypyridy  cAPR  a8192-81980 v143 a<p>We have synthesized a new photoactive rhenium(I)-complex having a pendant catechol functionality [Re(CO)3Cl(L)] (1) (L is 4-[2-(4′-methyl-2,2′-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) for studying the dynamics of the interfacial electron transfer between nanoparticulate TiO2 and the photoexcited states of this Re(I)-complex using femtosecond transient absorption spectroscopy. Our steady state absorption studies revealed that complex 1 can bind strongly to TiO2 surfaces through the catechol functionality with the formation of a charge transfer (CT) complex, which has been confirmed by the appearance of a new red-shifted CT band. The longer wavelength absorption band for 1, bound to TiO2 through the proposed catecholate functionality, could also be explained based on the DFT calculations. Dynamics of the interfacial electron transfer between 1 and TiO2 nanoparticles was investigated by studying kinetics at various wavelengths in the visible and near infrared regions. Electron injection into the conduction band of the nanoparticulate TiO2 was confirmed by detection of the conduction band electron in TiO2 (Image ID:c2cp24105f-t1.gif) and the cation radical of the adsorbed dye (1˙+) in real time as monitored by transient absorption spectroscopy. A single exponential and pulse-width limited (&lt;100 fs) electron injection was observed. Back electron transfer dynamics was determined by monitoring the decay kinetics of 1˙+ and Image ID:c2cp24105f-t2.gif.</p>1 aKar, Prasenjit1 aBanerjee, Tanmay1 aVerma, Sandeep1 aSen, Anik1 aDas, Amitava1 aGanguly, Bishwajit1 aGhosh, Hirendra, N.  uhttps://library.ncl.res.in/content/photosensitization-nanoparticulate-tio2-using-rei-polypyridyl-complex-studies-interfacial01847nas a2200181   4500008004100000245009700041210006900138260000800207300001600215490000600231520119900237100001901436700001901455700002101474700001701495700002401512856012901536       2012                        eng d00aSequential energy and electron transfer in polynuclear complex sensitized TiO2 nanoparticles0 aSequential energy and electron transfer in polynuclear complex s  cMAY  a1543–15480 v33 a<p>Polynuclear–polypyridyl complexes exhibit a directional energy-transfer property that can improve their photosensitization activity. In the present work, the energy-transfer process is explored in a trinuclear Ru2∧Os1 complex using transient absorption spectroscopy. This study reveals an efficient excitation energy transfer from the terminal (RuII complex) to the core (OsII complex) region in the ultrafast time domain (400 fs–40 ps). The excitation energy funnel is useful in improving the functionalized core activity. This is evidenced in an interfacial electron-transfer study of Ru2∧Os1, Ru2∧Ru1, and Os1 complex sensitized TiO2 nanoparticle (TiO2 NP) systems. The intramolecular energy transfer causes sequential excitation of the core part of the Ru2∧Os1 complex, which leads to multiexponential electron injection into TiO2 NP. Besides this, the electronic coupling between the metal ion centers stabilizes the positive charge within the trinuclear complex, which results in a slow charge recombination reaction. This study shows that polynuclear complexes can be very useful for their panchromatic effects, unidirectional energy- and electron-transfer properties.</p>1 aVerma, Sandeep1 aKar, Prasenjit1 aBanerjee, Tanmay1 aDas, Amitava1 aGhosh, Hirendra, N.  uhttps://library.ncl.res.in/content/sequential-energy-and-electron-transfer-polynuclear-complex-sensitized-tio2-nanoparticles01787nas a2200241   4500008004100000022001400041245013600055210006900191260007700260300001600337490000700353520085500360653002401215653001901239653002901258653002101287653002801308100001801336700002101354700002001375700001901395856013101414       2014                        eng d  a0947-653900aEvolution of an adenine-copper cluster to a highly porous cuboidal framework: solution-phase ripening and gas-adsorption properties0 aEvolution of an adeninecopper cluster to a highly porous cuboida  aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcSEP  a12262-122680 v203 a<p>The synthesis and directed evolution of a tetranu-clear copper cluster, supported by 8-mercapto-N9-propyladenine ligand, to a highly porous three-dimensional cubic framework in the solid state is reported. The structure of this porous framework was unambiguously characterized by Xray crystallography. The framework contains about 62% solvent-accessible void; the presence of a free exocyclic amino group in the porous framework facilitates reversible adsorption of gas and solvent molecules. Oriented growth of framework in solution was also tracked by force and scanning electron microscopy studies, leading to identification of an intriguing ripening process, over a period of 30 days, which also revealed formation of cuboidal aggregates in solution. The elemental composition of these cuboidal aggregates was ascertained by EDAX analysis.</p>10acuboidal frameworks10agas adsorption10ametal-organic frameworks10aOstwald ripening10asolution-phase ripening1 aVenkatesh, V.1 aPachfule, Pradip1 aBanerjee, Rahul1 aVerma, Sandeep  uhttps://library.ncl.res.in/content/evolution-adenine-copper-cluster-highly-porous-cuboidal-framework-solution-phase-ripening-001840nas a2200169   4500008004100000022001400041245012100055210006900176260007100245300001600316490000800332520113900340100001901479700001701498700002401515856013101539       2014                        eng d  a1932-744700aSize quantization effects on interfacial electron transfer dynamics in Ru(II)-polypyridyl complex sensitized ZnO QDs0 aSize quantization effects on interfacial electron transfer dynam  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC  a28898-289050 v1183 a<p>Quantum-size confinement in semiconductor material offers size based tunability of interband gap energy as well as intraband sublevels. In this work, size quantization of wide bandgap ZnO quantum dots has been explored in the study of interfacial charge separation reaction using a catechol functionalized Ru(II)polypyridyl complex as a photosensitizer molecule. Femtosecond time-resolved transient absorption studies have revealed multiple electron injection events based on discrete conduction band states of ZnO QDs. The electron injection rates have been rationalized for quantum confinement effects owing to different sizes of ZnO QDs. Furthermore, the size dependency of the intrinsic lifetime of electrons injected into discrete energy levels of ZnO QDs has been revealed in charge recombination reaction with the Ru(III)polypyridyl complex cation. The charge recombination dynamics reveals a competing trend of carrier confinement and carrier leak upon reducing particle size. This study shows the optimization of finite size effects in achieving better interfacial charge separation at the dye/semiconductor interface.</p>1 aVerma, Sandeep1 aDas, Amitava1 aGhosh, Hirendra, N.  uhttps://library.ncl.res.in/content/size-quantization-effects-interfacial-electron-transfer-dynamics-ruii-polypyridyl-complex-001915nas a2200241   4500008004100000022001400041245007500055210006900130260011000199300001400309490000600323520105000329100001701379700002301396700002401419700001801443700002001461700002601481700001801507700001901525700002001544856010901564       2015                        eng d  a2041-652000aChemical sensing in two dimensional porous covalent organic nanosheets0 aChemical sensing in two dimensional porous covalent organic nano  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcAPR  a3931-39390 v63 a<p>Two new imide-based crystalline, porous, and chemically stable covalent organic frameworks (COFs) (TpBDH and TfpBDH) have been successfully synthesized employing solvothermal crystallization route. Furthermore, thin layered covalent organic nanosheets (CONs) were derived from these bulk COFs by the simple liquid phase exfoliation method. These 2D CONs showcase increased luminescence intensity compared to their bulk counterparts (COFs). Notably, TfpBDH-CONs showcase good selectivity and prominent, direct visual detection towards different nitroaromatic analytes over TpBDH-CONs. Quite interestingly, TfpBDH-CONs exhibit a superior ``turn-on'' detection capability for 2,4,6-trinitrophenol (TNP) in the solid state, but conversely, they also show a ``turn-off'' detection in the dispersion state. These findings describe a new approach towards developing an efficient, promising fluorescence chemosensor material for both visual and spectroscopic detection of nitroaromatic compounds with very low [10(-5) (M)] analyte concentrations.</p>1 aDas, Gobinda1 aBiswal, Bishnu, P.1 aKandambeth, Sharath1 aVenkatesh, V.1 aKaur, Gagandeep1 aAddicoat, Matthew, A.1 aHeine, Thomas1 aVerma, Sandeep1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/chemical-sensing-two-dimensional-porous-covalent-organic-nanosheets-001939nas 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-101796nas a2200217   4500008004100000022001400041245008100055210006900136260009000205300000900295490000600304520100700310100002401317700001801341700002501359700001901384700001801403700001901421700002001440856011801460       2015                        eng d  a2041-172300aSelf-templated chemically stable hollow spherical covalent organic framework0 aSelftemplated chemically stable hollow spherical covalent organi  aMACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLANDbNATURE PUBLISHING GROUPcAPR  a67860 v63 a<p>Covalent organic frameworks are a family of crystalline porous materials with promising applications. Although active research on the design and synthesis of covalent organic frameworks has been ongoing for almost a decade, the mechanisms of formation of covalent organic frameworks crystallites remain poorly understood. Here we report the synthesis of a hollow spherical covalent organic framework with mesoporous walls in a single-step template-free method. A detailed time-dependent study of hollow sphere formation reveals that an inside-out Ostwald ripening process is responsible for the hollow sphere formation. The synthesized covalent organic framework hollow spheres are highly porous (surface area similar to 1,500m(2) g(-1)), crystalline and chemically stable, due to the presence of strong intramolecular hydrogen bonding. These mesoporous hollow sphere covalent organic frameworks are used for a trypsin immobilization study, which shows an uptake of 15.5 mu mol g(-1) of trypsin.</p>1 aKandambeth, Sharath1 aVenkatesh, V.1 aShinde, Digambar, B.1 aKumari, Sushma1 aHalder, Arjun1 aVerma, Sandeep1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/self-templated-chemically-stable-hollow-spherical-covalent-organic-framework-100898nas a2200253   4500008004100000245011700041210006900158260000800227300001400235490000700249100001800256700002400274700002300298700002000321700002100341700002600362700002600388700002500414700001700439700001800456700001900474700002000493856013100513       2016                        eng d00aDecoding the morphological diversity in two dimensional crystalline porous polymers by core planarity modulation0 aDecoding the morphological diversity in two dimensional crystall  cJUN  a7806-78100 v551 aHalder, Arjun1 aKandambeth, Sharath1 aBiswal, Bishnu, P.1 aKaur, Gagandeep1 aRoy, Neha, Chaki1 aAddicoat, Matthew, A.1 aSalunke, Jagadish, K.1 aBanerjee, Subhrashis1 aVanka, Kumar1 aHeine, Thomas1 aVerma, Sandeep1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/decoding-morphological-diversity-two-dimensional-crystalline-porous-polymers-core-planarity01603nas a2200169   4500008004100000245008200041210006900123260000800192300001600200490000800216520102100224100001901245700001601264700001701280700002401297856011201321       2016                        eng d00aProton-coupled electron transfer in a hydrogen-bonded charge transfer complex0 aProtoncoupled electron transfer in a hydrogenbonded charge trans  cOCT  a10780-107850 v1203 aA proton-coupled electron transfer (PCET) reaction in a hydrogen bonded charge-transfer (CT) complex of 4-([2,2'-bipyridin]-4-yl)phenol (bpy-phenol) with a F- ion has been investigated by ultrafast time-resolved transient absorption spectroscopy. The phenolic receptor molecule, bpy-phenol, binds to the F- ion through a hydrogen bond and senses the F- ion-via the Stokes-shifted CT band. Upon photoexcitation, CT from the phenol residue to the bpy residue promotes proton transfer from the phenol radical cation (ArOH center dot+) to the fluoride ion at ultrafast time scales of <150 fs (instrument response function limited) and 3 ps, separately. The fast and slow proton-transfer times are linked to two different types of hydrogen-bonding networks between the phenol residue and fluoride ion. Crystalline water in the fluoride salt hydrates mediates the proton-transfer reaction. This work demonstrates the participation of a hydrogen-bonded water bridge within a PCET reaction in a water restricted environment.1 aVerma, Sandeep1 aAute, Sunil1 aDas, Amitava1 aGhosh, Hirendra, N.  uhttps://library.ncl.res.in/content/proton-coupled-electron-transfer-hydrogen-bonded-charge-transfer-complex02011nas a2200289   4500008004100000022001400041245008000055210006900135260007100204300001400275490000800289520102800297100001901325700002401344700002301368700002201391700003001413700002101443700002001464700002501484700002101509700001901530700001501549700002201564700002001586856011501606       2017                        eng d  a0002-786300aSelf-exfoliated guanidinium-based ionic covalent organic nanosheets (iCONs)0 aSelfexfoliated guanidiniumbased ionic covalent organic nanosheet  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a2823-28280 v1383 a<p>Covalent organic nanosheets (CONs) have emerged as functional two-dimensional materials for versatile applications. Although pi-pi stacking between layers, hydrolytic instability, possible restacking prevents their exfoliation on to few thin layered CONs from crystalline porous polymers. We anticipated rational designing of a structure by intrinsic ionic linker could be the solution to produce self-exfoliated CONs without external stimuli. In an attempt to address this issue, we have synthesized three self-exfoliated guanidinium halide based ionic covalent organic nanosheets (iCONs) with antimicrobial property. Self-exfoliation phenomenon has been supported by molecular dynamics (MD) simulation as well. Intrinsic ionic guanidinium unit plays the pivotal role for both self-exfoliation and antibacterial property against both Gram-positive and Gram-negative bacteria. Using such iCONs, we have devised a Mixed matrix membrane which could be useful for antimicrobial coatings with plausible medical benefits.</p>1 aMitra, Shouvik1 aKandambeth, Sharath1 aBiswal, Bishnu, P.1 aKhayum, Abdul, M.1 aChoudhury, Chandan, Kumar1 aMehta, Mihir, R.1 aKaur, Gagandeep1 aBanerjee, Subhrashis1 aPrabhune, Asmita1 aVerma, Sandeep1 aRoy, Sudip1 aKharul, Ulhas, K.1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/self-exfoliated-guanidinium-based-ionic-covalent-organic-nanosheets-icons-0