@article {42538, title = {Competitive binding of Ba2+and Sr2+ to 18-crown-6 in a receptor with a 1-methoxyanthraquinone analogue as the other binding site}, journal = {Europian Journal of Inorganic Chemistry}, year = {2011}, month = {OCT}, pages = {4680{\textendash}4690}, abstract = {

Owing to their immense biological significance, development of sensors for the selective detection of alkaline earth metal ions has attracted vast research interest. In this article we have reported the synthesis, characterisation and ion binding studies of a new RuII-polypyridyl-crown-anthraquinone complex (5). Studies confirm selective binding of BaII, SrII and CaII ions, with Kmath image \> Kmath image \>\> Kmath image, over all other metal ions, to the crown ether moiety and not to the methoxy anthraquinone component, the latter being the second binding site available and known for its affinity towards alkaline earth metal ions from one of our previous reports.

}, doi = {10.1002/ejic.201100472}, author = {Banerjee, Tanmay and Suresh, Moorthy and Ghosh, Hirendra N. and Das, Amitava} } @article {42526, title = {Diamine derivative of a ruthenium(II)-polypyridyl complex for chemodosimetric detection of nitrite ion in aqueous solution}, journal = {Inorganica Chimica Acta}, volume = {372}, year = {2011}, month = {FEB}, pages = {115{\textendash}119}, abstract = {

Nitrite is quite an abundant anion in the environment. It, however, becomes toxic to human life, as well as aquatic animals when present above the permissible concentration level. We have reported here a Ru(II)-polypyridyl-based complex (1) for chemodosimetric detection of nitrite ion in aqueous solution. Formation of the new triazole based complex, generated by reaction of 1 and N2O3, is ascertained by comparing its properties with a presynthesised triazole complex.

}, doi = {10.1016/j.ica.2011.01.066}, author = {Ghosh, Amrita and Das, Priyadip and Saha, Sukdeb and Banerjee, Tanmay and Bhatt, Harshad B. and Das, Amitava} } @article {42540, title = {Interfacial electron transfer dynamics of two newly synthesized catecholate bound ruII polypyridyl-based sensitizers on TiO2 nanoparticle surface - a femtosecond pump probe spectroscopic study}, journal = {Europian Journal of Inorganic Chemistry}, year = {2011}, month = {SEP}, pages = {4187{\textendash}4197}, abstract = {

Two new catecholate-bound RuII{\textendash}polypyridine based sensitizers, (2,2'-bipyridine){ethyl 3-(4-hydroxyphenyl)-2-[(4'-methyl-2,2'-bipyridinyl-4-carbonyl)amino]propionate}{4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol)}ruthenium(II) hexafluorophosphate (5) and [(2,2'-bipyridine)-(4-2,2'-bipyridinyl-4-yl-phenol)-(4-{2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl}benzene-1,2-diol)]ruthenium(II) hexafluorophosphate (6) with secondary electron-donating groups (tyrosine and phenol, respectively) were synthesized and characterized. Steady-state optical absorption and emission studies confirm strong coupling between the sensitizers and TiO2 nanoparticles. Femtosecond visible transient absorption spectroscopy has been employed to study interfacial electron transfer (IET) dynamics in the dye{\textendash}nanoparticle systems to explore the influence of the secondary electron-donating groups on IET dynamics. Electron injection into the conduction band of nanoparticulate TiO2 has been confirmed by detection of the conduction band electrons in TiO2 ([e{\textendash}]TiO2CB) and radical cation of the adsorbed dye (D{\textperiodcentered}+) in real time monitored by transient absorption spectroscopy. A single exponential and pulse-width limited (\< 100 fs) electron injection has been observed. Back electron transfer (BET) dynamics have been studied by monitoring the decay kinetics of the injected electron in the conduction band of TiO2 and by the recovery of the ground state bleach. BET dynamics in dye{\textendash}TiO2 systems for complexes 5 and 6 have been compared with those of [bis(2,2'-bpy)-(4-{2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl}benzene-1,2-diol)]ruthenium(II) hexafluorophosphate (7), which does not have a secondary electron-donating group.

}, doi = {10.1002/ejic.201100411}, author = {Banerjee, Tanmay and Rawalekar, Sachin and Das, Amitava and Ghosh, Hirendra Nath} } @article {42522, title = {Urea/thiourea derivatives and Zn(II)-DPA complex as receptors for anionic recognition-a brief account}, journal = {Journal of Chemical Sciences}, volume = {123}, year = {2011}, month = {OCT}, pages = {175{\textendash}186}, abstract = {

This review covers few examples of anion complexation chemistry, with a special focus on urea/thiourea-based receptors and Zn(II)-dipicolyl amine-based receptors. This article specially focuses on structural aspects of the receptors and the anions for obtaining the desire specificity along with an efficient receptor{\textendash}anion interaction. Two types of receptors have been described in this brief account; first one being the strong hydrogen bond donor urea/thiourea derivatives, which binds the anionic analytes through hydrogen bonded interactions; while, the second type of receptors are coordination complexes, where the coordination of the anion to the metal centre. In both the cases the anion binding modulate the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and thereby the spectroscopic response. Appropriate choice of the signalling unit may allow probing the anion binding phenomena through visual detection.

}, doi = {10.1007/s12039-011-0151-y}, author = {Das, Priyadip and Mahato, Prasenjit and Ghosh, Amrita and Mandal, Amal Kumar and Banerjee, Tanmay and Saha, Sukdeb and Das, Amitava} } @article {42516, title = {Photosensitization of nanoparticulate TiO2 using a Re(I)-polypyridyl complex: studies on interfacial electron transfer in the ultrafast time domain}, journal = {Physical Chemistry Chemical Physics}, volume = {14}, year = {2012}, month = {APR}, pages = {8192-8198}, abstract = {

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 (\<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.

}, doi = {10.1039/C2CP24105F}, author = {Kar, Prasenjit and Banerjee, Tanmay and Verma, Sandeep and Sen, Anik and Das, Amitava and Ganguly, Bishwajit and Ghosh, Hirendra N.} } @article {42510, title = {Sequential energy and electron transfer in polynuclear complex sensitized TiO2 nanoparticles}, journal = {Journal of Physical Chemistry Letters}, volume = {3}, year = {2012}, month = {MAY}, pages = {1543{\textendash}1548}, abstract = {

Polynuclear{\textendash}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{\textendash}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.

}, doi = {10.1021/jz3005305}, author = {Verma, Sandeep and Kar, Prasenjit and Banerjee, Tanmay and Das, Amitava and Ghosh, Hirendra N.} } @article { ISI:000324758700022, title = {Interfacial charge recombination of Os(II)-polypyridyl-resorcinol complex on oleic acid capped TiO2 surface: what determines the dynamics?}, journal = {New Journal of Chemistry}, volume = {37}, number = {10}, year = {2013}, month = {JUL}, pages = {3100-3108}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Femtosecond transient absorption spectroscopic studies of an osmium(II)-polypyridyl-resorcinol complex, 1, on oleic acid capped TiO2 have been carried out and the results have been compared with our previous studies on poly(vinyl) alcohol capped TiO2. While on both these surfaces the complex exhibits a single exponential \<120 fs injection, the back electron transfer reaction is slower on the oleic acid capped TiO2 surface early on while it is faster on the same surface at longer times than on poly(vinyl)alcohol capped TiO2. The probable origin of these disparate observations has been analyzed.

}, issn = {1144-0546}, doi = {10.1039/c3nj00550j}, author = {Banerjee, Tanmay and Das, Amitava and Ghosh, Hirendra N.} } @article { ISI:000324928000035, title = {New receptor with a FRET based fluorescence response for selective recognition of fumaric and maleic acids in aqueous medium}, journal = {Chemical Communications}, volume = {49}, number = {84}, year = {2013}, month = {AUG}, pages = {9818-9820}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Preferential binding of a new reagent to fumaric acid could be utilized for its estimation in aqueous medium and in commercial fruit juice.

}, issn = {1359-7345}, doi = {10.1039/c3cc45051a}, author = {Reddy, Upendar G. and Lo, Rabindranath and Roy, Sovan and Banerjee, Tanmay and Ganguly, Bishwajit and Das, Amitava} } @article {42491, title = {Newly designed resorcinolate binding for Ru(II)- and Re(I)- polypyridyl complexes on oleic acid capped tio2 in non-aqueous solvent: prolonged charge separation and substantial thermalized 3MLCT injection}, journal = {Journal of Physical Chemistry C}, volume = {117}, year = {2013}, month = {JAN}, pages = {3084{\textendash}3092}, abstract = {

Femtosecond pump{\textendash}probe spectroscopic studies on a series of newly synthesized resorcinol-based Ru(II) and Re(I) complexes on oleic acid capped TiO2 nanoparticles have been carried out in chloroform, and the results are compared with those of the catechol analogues. The ruthenium complex shows biexponential injection; the second component arises due to injection from the thermally equilibrated 3MLCT states as a result of a weaker strength of the resorcinolate binding. Also, in comparison with catechol binding, as a result of a greater diffusion of the injected electrons into TiO2, the back electron transfer (BET) is slowed down significantly for the ruthenium complex. These are distinctive observations for any mononuclear ruthenium{\textendash}polypyridyl{\textendash}enediol complex reported thus far. However, the rhenium complex educes single exponential ultrafast injection (\<120 fs) because of apparent injection in a high density of states and shows the most prominent results with \~{}50\% slowdown in the charge recombination rate as compared to the analogous catechol bound system. These results exemplify the probable development of highly capable sensitizer dyes with resorcinol as the anchoring group for the development of efficient dye-sensitized solar cells.

}, doi = {10.1021/jp310570n}, author = {Banerjee, Tanmay and Kaniyankandy, Sreejith and Das, Amitava and Ghosh, Hirendra Nath} } @article {42488, title = {Synthesis, steady-state, and femtosecond transient absorption studies of resorcinol bound ruthenium(ii)- and osmium(ii)-polypyridyl complexes on nano-TiO2 surface in water}, journal = {Inorganic Chemistry}, volume = {52}, year = {2013}, month = {APR}, pages = {5366{\textendash}5377}, abstract = {

The synthesis of two new ruthenium(II)- and osmium(II)-polypyridyl complexes 3 and 4, respectively, with resorcinol as the enediol anchoring moiety, is described. Steady-state photochemical and electrochemical studies of the two sensitizer dyes confirm strong binding of the dyes to TiO2 in water. Femtosecond transient absorption studies have been carried out on the dye{\textendash}TiO2 systems in water to reveal \<120 fs and 1.5 ps electron injection times along with 30\% slower back electron transfer time for the ruthenium complex 3. However, the corresponding osmium complex 4 shows strikingly different behavior for which only a \<120 fs ultrafast injection is observed. Most remarkably, the back electron transfer is faster as compared to the corresponding catechol analogue of the dye. The origin and the consequences of such profound effects on the ultrafast interfacial dynamics are discussed. This Article on the electron transfer dynamics of the aforesaid systems reinforces the possibility of resorcinol being explored and developed as an extremely efficient binding moiety for use in dye-sensitized solar cells.

}, doi = {10.1021/ic4003548}, author = {Banerjee, Tanmay and Kaniyankandy, Sreejith and Das, Amitava and Ghosh, Hirendra Nath} } @article { ISI:000341282100018, title = {New Ru(II)/Os(II)-polypyridyl complexes for coupling to TiO2 surfaces through acetylacetone functionality and studies on interfacial electron-transfer dynamics}, journal = {Dalton Transactions}, volume = {43}, number = {36}, year = {2014}, month = {SEP}, pages = {13601-13611}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

New Ru(II)- and Os(II)-polypyridyl complexes have been synthesized with pendant acetylacetone (acac) functionality for anchoring on nanoparticulate TiO2 surfaces with a goal of developing an alternate sensitizer that could be utilized for designing an efficient dye-sensitized solar cell (DSSC). Time-resolved transient absorption spectroscopic studies in the femtosecond time domain have been carried out. The charge recombination rates are observed to be very slow, compared with those for strongly coupled dye molecules having catechol as the anchoring functionality. The results of such studies reveal that electron-injection rates from the metal complex-based LUMO to the conduction band of TiO2 are faster than one would expect for an analogous complex in which the chromophoric core and the anchoring moiety are separated with multiple saturated C-C linkages. Such an observation is rationalized based on computational studies, and a relatively smaller spatial distance between the dye LUMO and the TiO2 surface accounted for this. Results of this study are compared with those for analogous complexes having a gem-dicarboxy group as the anchoring functionality for covalent binding to the TiO2 surface to compare the role of binding functionalities on electron-transfer dynamics.

}, issn = {1477-9226}, doi = {10.1039/c4dt01571a}, author = {Banerjee, Tanmay and Biswas, Abul Kalam and Sahu, Tuhin Subhra and Ganguly, Bishwajit and Das, Amitava and Ghosh, Hirendra Nath} } @article { ISI:000332188100002, title = {Superior grafting and state-of-the-art interfacial electron transfer rates for newly designed geminal dicarboxylate bound ruthenium(II)- and osmium(II)-polypyridyl dyes on TiO2 nanosurface}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {8}, year = {2014}, month = {FEB}, pages = {3864-3877}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Two new Ru(II)-/Os(II)-polypyridyl based sensitizer dyes with geminal dicarboxylic acid group as the binding unit for superior grafting of the dye to TiO2 have been designed and synthesized. Steady-state photochemical studies of the two sensitizer dyes in presence of TiO2 in water confirm strong binding of the dyes to TiO2. Femtosecond transient absorption studies of these newly synthesized dyes on TiO2 nanosurface have been carried out in water and the results have been compared with those for the corresponding 4,4{\textquoteright}-dicarboxy-2,2{\textquoteright}-bipyridine analogues of the dyes. While the charge recombination rates are considerably slower, interestingly, the electron injection rates are very fast for multiple saturated C-C linkages present between the chromophoric core and the anchoring moiety. The origin and the consequences of such profound effects on the ultrafast interfacial dynamics are discussed. This is the first report on the ultrafast transient absorption studies of dyes with geminal dicarboxylic acid binding groups, which we believe will add significantly to the present research efforts toward the development of robust and efficient dyes for use in dye solar applications.

}, issn = {1932-7447}, doi = {10.1021/jp4077917}, author = {Banerjee, Tanmay and Biswas, Abul Kalam and Reddy, Upendar G. and Sahu, Tuhin Subhra and Das, Amitava and Ganguly, Bishwajit and Ghosh, Hirendra Nath} } @article { ISI:000349942400010, title = {Ultrafast electron injection, hole transfer, and charge recombination dynamics in cdse QD super-sensitized Re(I)-polypyridyl complexes with catechol and resorcinol moiety: effect of coupling}, journal = {Journal of Physical Chemistry C}, volume = {119}, number = {7}, year = {2015}, month = {FEB}, pages = {3522-3529}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Ultrafast charge-transfer dynamics have been demonstrated in CdSe quantum dots (QD) using two Re(I)-polypyridyl complexes having pendent catechol (Re1,2) and resorcinol (Re1,3) as the sensitizer molecules. The energy level diagram of CdSe QD and Re1,2 and Re1,3 sensitizer reveals that photoexcited hole of CdSe QD can be transferred to both Re1,2 and Re1,3 molecule, and photoexcited Re1,2 and Re1,3 can inject electron in the conduction band, which has been confirmed by steady-state and time-resolved photoluminescence studies with selective photoexcitation. Femtosecond transient absorption studies have been carried out to monitor charge-transfer dynamics in early time scale. Transient absorption spectra show formation of cation radicals for both Re1,2 and Re1,3 in the 550-650 nm region with a peak at 590 nm region and broad absorption in the 650-1000 nm region, which can be attributed to photoexcited electron in the conduction band of CdSe QD. Charge recombination was determined by monitoring the decay of cation radicals as well as decay of an electron and found to be slower in the Re1,3/CdSe system as compared to that of the Re1,2/CdSe system, which is due to weaker electronic coupling in the former system.

}, issn = {1932-7447}, doi = {10.1021/jp5122068}, author = {Debnath, Tushar and Maity, Partha and Banerjee, Tanmay and Das, Amitava and Ghosh, Hirendra N.} } @article { ISI:000375969000056, title = {Charge delocalization in the cascade band structure CdS/CdSe and CdS/CdTe core-shell sensitized with Re(I)-polypyridyl complex}, journal = {Journal of Physical Chemistry C}, volume = {120}, number = {18}, year = {2016}, month = {MAY}, pages = {10051-10061}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Charge-carrier dynamics of CdS quantum dot (QD) and CdS/CdSe type-I and CdS/CdTe type-II core shell nanocrystals (NCs) sensitized with a Re(I)-polypyridyl complex have been carried with special emphasis on studies on carrier delocalization and the role of Re-complex as a hole acceptor and sensitizer molecule. Our investigation confirmed photoexcited hole transfer from CdS and CdS/CdSe to the Re-complex, while no hole transfer was observed in the CdS/CdTe Re-complex system. This was rationalized by the evaluation of the relative energy levels, which revealed that such hole migration was not energetically favorable due to low-lying highest occupied molecular orbital (HOMO) of the Re-complex as compared with the valence band (VB) of CdTe shell; however, luminescence quenching from upper excited states of Re-complex was observed in the presence of all three QD and core shell systems, which has been attributed to electron injection from hot state (energetically higher than the LUMO state) of the Re-complex to the conduction band (CB) of the QDs. Transient absorption (lambda(pump) = 400 nm, lambda(probe) = 450-750 nm) spectra recorded for Re complex-sensitized CdS and CdS/CdSe composite in the femtosecond time domain revealed a broad transient absorption band in the 580-750 nm region with a peak around 595 nm, and this was attributed to the cation radical formation for Re-complex, either by capturing photoexcited hole from the NCs or by injecting electron to the CB of the NCs. As anticipated, no such spectrum was observed for the CdS/CdTe Re-complex composite system after 400 nm excitation. Electron injection from photoexcited Re-complex to CdS QD and CdS/CdSe core shell was found to be \<100 fs, while the hole transfer from photoexcited CdS QD and CdS/CdSe core shell to Re-complex took place within the time scale of 900 fs and 2.5 ps, respectively.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.6b01654}, author = {Maity, Partha and Debnath, Tushar and Banerjee, Tanmay and Das, Amitava and Ghosh, Hirendra N.} }