@article { ISI:000265529700034, title = {Density functional investigation of relativistic effects on the structure and reactivity of tetrahedral gold clusters}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {17}, year = {2009}, month = {APR}, pages = {7101-7106}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The influence of relativistic effects on the structure, vibrational modes, and reactivity of recently discovered tertrahedral gold clusters (Au(19) and Au(20)) are investigated using density functional methods. The intramolecular reactivity of the clusters was analyzed using density functional-based reactivity descriptors. The work shows that whereas the structural properties and vibrational modes are considerably affected by the relativistic effects, the reactivity trends based on Fukui function calculation on various atoms within this cluster remain unaffected by the absence or presence of relativistic effects. The reactivity descriptors reveal that the vertex atoms are the most reactive ones in Au(20) toward a nucleophilic attack. On the other hand, atoms connecting the missing vertex edge with the pyramid base along with the vertex atom are the most reactive for a nucleophilic attack in Au(19). The atoms lying at the center of each face are favorable for an electrophilic attack in both cases. Interestingly, the atoms with a missing cap in Aulg are highly favorable for electrophilic attack, and Au(20) has more sites for a favorable nucleophilic attack.

}, issn = {1932-7447}, doi = {10.1021/jp9001884}, author = {De, Himadri Sekhar and Krishnamurty, Sailaja and Pal, Sourav} } @article { ISI:000341122200039, title = {Dinitrogen activation by silicon and phosphorus doped aluminum clusters}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {34}, year = {2014}, month = {AUG}, pages = {19869-19878}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

N-2 reduction is crucial for life, and very few catalysts are currently available to carry out this process at ambient temperature and pressure. In the present work, density functional theory based calculations reveal doped aluminum clusters to be highly reactive toward molecular nitrogen and hence are prospective materials for its activation at low temperatures. Calculations on silicon and phosphorus doped aluminum clusters with 5-8 atoms demonstrate an enhanced N-2 activation with respect to their pristine ground state and high energy counterparts. This increased efficiency of N-2 activation by doped ground state Al clusters is corroborated by an increment of the N N bond length, a red shift in N N bond stretching frequency, and adsorption energy (E-ad). Ab initio molecular-dynamics simulations demonstrate consequential efficiency of doped clusters toward dinitrogen activation at finite temperature. The ability of doped clusters toward activation of molecular nitrogen is site and shape sensitive. In short, this theoretical study highlights the critical role of doping foreign impurities for future endeavors in the design of cost-effective and efficient catalysts for N-2 activation at ambient temperatures. This observation may spur further studies in the field of aluminum nanocatalysis by doping silicon and phosphorus atom in aluminum clusters.

}, issn = {1932-7447}, doi = {10.1021/jp505700a}, author = {Das, Susanta and Pal, Sourav and Krishnamurty, Sailaja} } @article { ISI:000372756700003, title = {DFT based assay for tailor-made terpyridine ligand-metal complexation properties}, journal = {Molecular Simulations}, volume = {42}, number = {8}, year = {2016}, month = {MAY}, pages = {618-627}, publisher = {TAYLOR \& FRANCIS LTD}, type = {Article}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

Electron-rich terpyridine ligand and its metal complexes have a potential to grow as responsive surfaces by adapting their physicochemical properties as a function of environment. The responsiveness is brought about by judicious molecular level designing that is currently hindered due to lack of information and control on terpyridine (TPy)-metal (M) interactions at single molecule level. So far there is no organised understanding on the binding of different metals with TPy ligand and ways to modulate it. Being a large conjugated [GRAPHICS] system, TPy has a large scope to be functionalised with electron exchanging groups to alter its electronic structure and consequently its binding with metal atoms. In first report of such a kind, using density functional theory (DFT), we demonstrate that convenient modulation of TPy-M binding is possible through functionalisation of TPy for [GRAPHICS] , Ru, Fe, Mo and Au. Electron donating groups viz., CH [GRAPHICS] , OCH [GRAPHICS] , C [GRAPHICS] H [GRAPHICS] , NH [GRAPHICS] and electron withdrawing groups viz., CF [GRAPHICS] , COOH, CN and NO [GRAPHICS] are considered for functionalisation of TPy ligand. Significantly, the present work focuses on the functionalisation at 4 and 4 [GRAPHICS] positions of TPy molecule. The role of such a functionalisation in influencing the ligands structure-property correlation is missing in the literature to the best of our knowledge. The present investigation quantifies that by pertinent functionalisation of TPy, TPy-M binding energies can be modified up to [GRAPHICS] 60kcal/mol. Our results reveal that functionalisation leads to a considerable charge redistribution within the TPy-M complex with carbon atoms in pyridine rings functioning as major electron sink/source with a corresponding red/blue shift of [GRAPHICS] stretching frequency. This modifies the red-ox, optical and other chemical properties of TPy-M complexes. In brief, the present report illustrates a way to design ligands such as TPy for diverse applications through tailor-made functionalisation using electronic structure methodology.

}, keywords = {Binding energy, charge redistribution, Density functional theory, functionalisation, Metal organic complexes, metal-ligand interactions, terpyridine}, issn = {0892-7022}, doi = {10.1080/08927022.2015.1067368}, author = {Joshi, Krati and Krishnamurty, Sailaja and Singh, Iksha and Selvaraj, Kaliaperumal} } @article {44123, title = {Dissociative adsorption of molecular hydrogen on BN-doped graphene-supported aluminum clusters}, journal = {Journal of Physical Chemistry C}, volume = {121}, year = {2017}, month = {NOV}, pages = {26493-26498}, type = {Article}, abstract = {The present work demonstrates dissociative adsorption of molecular hydrogen on supported and unsupported aluminum Wclusters (Al-n, n = 4-8, 13) using density functional theory based calculations. The studies reveal that the presence of a BN-doped graphene surface support reduces the dissociative adsorption barrier of the bond in molecular hydrogen on even atom clusters. In particular, supported Al-6 demonstrates a barrier-less dissociative adsorption toward the H-2 molecule. These results demonstrate the excellent potential of supported Al nanoparticles for hydrogen storage and also the potential of doped graphene systems are catalyzing supports.}, doi = {10.1021/acs.jpcc.7b07789}, author = {Kumar, Deepak and Krishnamurty, Sailaja and Pal, Sourav} } @article {45371, title = {Dissociative chemisorption of hydrogen molecules on defective graphene-supported aluminium clusters: a computational study}, journal = {Physical Chemistry Chemical Physics }, volume = {20}, year = {2018}, month = {NOV}, pages = {26506-26512}, type = {Article}, abstract = {

Using periodic density functional theory-based calculations, in the present study, we address the chemical bonding between aluminium clusters (Al-n, n = 4-8 and 13) and monovacant defective graphene. The adsorption strength of the above-mentioned aluminium clusters is fivefold (approximate to 3 to 5 eV) higher on defective graphene as compared to the earlier reported values on non-defective graphene and BN-doped graphene. The Bader charge analysis and different charge densities reveal that this adsorption is driven by significant charge transfer from the Al clusters to defective graphene. Thus, chemisorbed Al clusters demonstrate high activity towards dissociative adsorption of molecular hydrogen.

}, issn = { 1463-9076}, doi = {10.1039/c8cp05711g}, author = {Kumar, Deepak and Govindaraja, Thillai and Krishnamurty, Sailaja and Kaliaperumal, Selvaraj and Pal, Sourav} } @article {46437, title = {Dinitrogen activation on graphene anchored single atom catalysts: local site activity or surface phenomena}, journal = {Journal of Physical Chemistry C}, volume = {123}, year = {2019}, month = {NOV}, pages = {27492-27500}, type = {Article}, abstract = {

Catalysis on two-dimensional (2D) substrates with metal clusters or centers is generally dealt with as a surface phenomenon under the conjecture that the delocalized electron density is the driving force. When single atom catalysts (SACs) are anchored on such materials with delocalized electron density, for instance graphene, the stimulant for catalysis may be either the d-electrons on the metal or the system altogether. To understand the contributing factors of catalysis on such systems, a case study of dinitrogen (N-2) activation on Mo anchored graphene has been made by employing periodic and finite models of graphene. The periodic model represents a continuum of SACs anchored periodically on graphene, while the finite models are graphene nanoflakes of varying sizes and edge orientations. In addition to the physical aspects, such as size/finiteness of graphene, the influence of varying chemical compositions of the substrate on the activity is also evaluated by doping graphene with different B and N concentrations. This study, while clearly bringing out the connotation of regulating atomic composition of graphene substrate for dinitrogen activation, also surprisingly unveils the relative insignificance of varying the size and edge effects of the substrate. These features are highlighted through an analysis of red shift in the N-N stretching frequency, charge transfer to dinitrogen from the catalytic system, and structural and electronic characteristics of the catalytic system. The total and projected density of states plots reveal hybridization between the metal d orbitals and the p orbitals of carbon and nitrogen in the valence band. On the other hand, the frontier molecular orbital analysis also depicts a strong chemisorption of dinitrogen with the metal-graphene supports on account of direct hybridization between the d orbitals of the supported metal atom and the p orbitals of dinitrogen. The Bader and Lowdin charge distribution on the adsorbed dinitrogen in periodic and finite models shows the preeminence of local site over the surface activity.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.9b06757}, author = {Maibam, Ashakiran and Govindaraja, Thillai and Selvaraj, Kaliaperumal and Krishnamurty, Sailaja} } @article {47066, title = {Durable metalloporphyrin 2D-polymer for photocatalytic hydrogen and oxygen evolution from river and sea waters}, journal = {ChemCatChem}, volume = {13}, year = {2021}, month = {APR}, pages = {1717-1721}, type = {Article}, abstract = {

It is highly imaginary that the outcome of a combination of two complementary resources leads to answer an alarming global issue. One such possible example is the solar seawater splitting for {\textquoteleft}clean fuel{\textquoteright} H-2 generation. Since the catalytic activity and stability of the photocatalysts are substantially challenged in seawater, the design of an efficient and stable photocatalyst is highly desirable. Herein, we demonstrate the solar seawater splitting by a two-dimensional polymer catalyst derived from metalloporphyrin bearing multi-hydroxyl groups. A bimetallic (Co and Ni) porphyrin 2D-polymer exhibits excellent long-term durability of 15 cycles of H-2 and O-2 generation in 200 days from pure water without a considerable decrease in efficiency. Detailed studies using river and seawaters also show the reliable performance of the catalyst over repeated cycles. Here the deactivation modes of catalytic activity have been nullified by the layered metalloporphyrin polymer structure through stable pi-pi stacking, signifying the molecular design of 2D-polymer photocatalyst.

}, keywords = {2D-polymer, Photocatalyst, porphyrin, Self-assembly, water splitting}, issn = {1867-3880}, doi = {10.1002/cctc.202002039, Early Access Date = FEB 2021}, author = {Ranjeesh, Kayaramkodath Chandran and George, Leena and Maibam, Ashakiran and Krishnamurty, Sailaja and Babu, Sukumaran Santhosh} } @article {48299, title = {D-A-D-based unsymmetrical thiosquaraine dye for the dye-sensitized solar cells(dagger)}, journal = {Photochemistry and Photobiology}, volume = {99}, year = {2023}, month = {MAR}, pages = {529-537}, type = {Article}, abstract = {

In dye-sensitized solar cell, modulating the electronic properties of the sensitizer by varying the donor, pi-spacer, acceptor and anchoring groups help optimizing the structure of the dye for better device performance. Here, a donor-acceptor-donor-based unsymmetrical thiosquaraine sensitizer (SQ5S) has been designed and synthesized. Photophysical, electrochemical, theoretical and photovoltaic characterizations of SQ5S dye have been compared with its oxygen analog, SQ5. The incorporation of the sulfur atom in the acceptor unit of SQ5S dye showed an intense peak at 688 nm, which was 38 nm of red-shifted and showed the panchromatic light harvesting response with the onset of 850 nm compared with SQ5 dye. The LUMO and HOMO energy levels are well aligned with the conduction band of TiO2 and the redox potential of electrolyte for the charge injection and the dye-regeneration processes, respectively. Photovoltaic efficiency of 1.51\% (V-OC 610 mV, J(SC) 3.07 mA cm(-2), ff 81\%) has been achieved for SQ5S dye, whereas SQ5 showed the device performance of 5.43\% (V-OC 723 mV, J(SC) 9.3 mA cm(-2), ff 80\%). The decreased device performance for the dye SQ5S has been attributed to the favorable intersystem crossing process associated with the photoexcited SQ5S that reduces the driving force for the charge injection process.

}, issn = {0031-8655}, doi = {10.1111/php.13769}, author = {Jadhav, Avinash P. and Singh, Ambarish Kumar and Maibam, Ashakiran and Krishnamurty, Sailaja and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} } @article {49687, title = {Diamondoid all-carbon porous aromatic framework host for lithium-sulfur batteries}, journal = {Small}, volume = {21}, year = {2025}, month = {JUN}, pages = {2500388}, type = {Article}, abstract = {

Lithium-sulfur batteries (LSBs) hold incredible potential as next-generation energy storage systems. However, practical applications of LSBs are significantly hindered by several critical challenges. For the first time, scalable all-carbon porous 3D polymers (3DPs) that do not contain heteroatoms or functional groups and do not require post-functionalization are investigated as hosts in lithium-sulfur batteries, demonstrating enhanced cycling stability and overall battery performance. The pyrene-containing 3DP exhibits 75\% capacity retention after 600 cycles at 1 C and 52\% capacity retention after 1300 cycles at 0.2 C, better than phenyl comprising 3DP. Furthermore, even at higher sulfur loading (4.1 mg cm(-2)) with an electrolyte/sulfur ratio of 5 mu L mg(-1), pyrene 3DP displayed a high capacity of 600 mA h g(-1) and stable performance over 250 cycles with negligible capacity fade. The defined pore structure of 3DPs prevents the migration of polysulfides through physical confinement and the large pi -clouds of 3DPs interact with the negative charge-bearing polysulfides generated in charge-discharge cycles through anion-pi interaction. In this way, The design ensures that the host 3DPs interact with neutral sulfur and anionic polysulfides, resulting in an excellent performance.

}, keywords = {3D polymers, Batteries, Li-Sulfur battery, porous materials, pyrene}, issn = {1613-6810}, doi = {10.1002/smll.202500388}, author = {Kumar, Viksit and Javaregowda, Bharathkumar H. and Devasia, George and Narayanan, Aswini and Krishnamurty, Sailaja and Krishnamoorthy, Kothandam and Babu, Sukumaran Santhosh} }