Recent Publications View All

• Nain, S., Mukhopadhy Unravelling the Highest Magnetic Anisotropy Among all the nd-Shells in [WCp2]0 Metallocene Inorg. Chem. , 2024 , 63 , 7401–7411.

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Unravelling the Highest Magnetic Anisotropy Among all the nd-Shells in [WCp2]0 Metallocene



Authors:Nain, S., Mukhopadhyaya, A., and Ali, M. E.

Publication Details:Inorg. Chem.,2024, 63, 7401–7411

Abstract:
Single-molecule magnets (SMMs) with a large magnetization reversal barrier are predominated by the lanthanide systems due to their strong spin–orbit coupling (SOC). However, the transition metals have also emerged as potential contenders and the largest magnetic anisotropy has been identified for a cobalt system among any d-series-based SMMs (Bunting et al. Science 2018, 362, eaat7319). In this work, we have explored the magnetic anisotropy in highly axial ligand field systems of metallocene, having different d-subshell (3d4, 4d4, and 5d4). The wave function-based multireference methods including static and dynamic electron correlations have been employed to investigate the zero-field splitting (ZFS) parameters. Here, we report exceptionally large magnetic anisotropy for a 5d complex of [WCp2]0 with the highest energy barrier that is nearly twice as high as the previous record value for the Co complex. We have also observed that the axial ZFS parameter (D) is increasing down the group in the order of 3d < 4d < 5d, pertaining to a large SOC.

DOI Link: 10.1021/acs.inorgchem.4c00437

• Mukhopadhyaya, A., a Can Iron–Porphyrins Behave as Single-Molecule Magnets? J. Phys. Chem. A , 2024 , 128 , 2339–2348.

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Can Iron–Porphyrins Behave as Single-Molecule Magnets?



Authors:Mukhopadhyaya, A., and Ali, M. E.

Publication Details:J. Phys. Chem. A,2024, 128, 2339–2348

Abstract:


The study of magnetic properties, especially the magnetic anisotropy of iron–porphyrin complexes employing multiconfigurational methods, is quite challenging due to many strongly correlated electrons in nearly degenerate orbitals. However, a prerequisite for observing the magnetic anisotropy and slow magnetization relaxation, the zero-field splitting parameter, D, was experimentally observed decades ago for halide-based axially ligated penta-coordinate Fe(III)–porphyrins. In these complexes, the signs of D were reported mostly as positive; in a few cases, inconclusive signs of the D parameter were also mentioned. However, no ab initio calculations have been reported to shed light on this. Deciphering the electronic structure of these penta-coordinated complexes employing the complete active space self-consistent field method and N-electron valence second-order perturbation theory, we confirm the positive D values. However, a negative D value is highly desired to observe the single-molecule magnet properties without an external magnetic field, which we observed in the Fe(II)–porphyrin complexes with axial imidazole ligands instead of halide ligands. The detailed analysis of the multireference wave functions unravels the role of axial ligands in determining the sign and magnitude of the D parameters.

 

DOI Link: 10.1021/acs.jpca.4c00430

• Ali, S. and Ali, M. Broken edge spin symmetry induces a spin-polarized current in graphene nanoribbon J. Phys. D: Appl. Phys. , 2024 , 57 , 215001.

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Broken edge spin symmetry induces a spin-polarized current in graphene nanoribbon



Authors:Ali, S. and Ali, M. E.

Publication Details:J. Phys. D: Appl. Phys.,2024, 57, 215001

Abstract:
Zigzag graphene nanoribbons (ZGNRs) are known to possess spin moments at the hydrogen-terminated edge carbon atoms; thus, spin-polarized electron transmission is expected, while the current is longitudinally passed through the ZGNRs. However, in pristine ZGNRs, spin-polarized transmission is not observed due to symmetric anti-parallel distributions of the spin densities between the edges. Here, the hypothesis is that any physical or chemical process that breaks such anti-parallel spin symmetry can induce spin-polarized transmission in ZGNRs. In this work, we have established this proof-of-concept by depositing the trimethylenemethane (TMM) radical on 6ZGNRH and investigating the quantum transport properties by employing density functional theory in conjunction with the nonequilibrium Green’s function method. Although TMM has a high magnetic moment (2µB), it does not induce magnetization in 6ZGNRH when TMM is physisorbed. However, during the chemisorption of TMM, it forms the π − π bond with the 6ZGNRH in a particular geometric configuration, where the pz orbitals of carbon atoms of TMM have maximum overlap with the pz orbitals of carbon atoms of 6ZGNRH. The chemisorption of TMM transfers the spin moment to 6ZGNRH, which breaks the edge spin symmetry of pristine 6ZGNRH. The adsorption of the TMM radical results in transmission dips in the transmission spectra due to interference between localized states of TMM and 6ZGNRH states. This induces spin-polarized transmission with 60% spin-filtering efficiency at zero bias, which can further be enhanced up to 92% by applying a bias voltage of 1.0 V.

DOI Link: 0000-0002-2179-3033

• Saini, N.; Sharma,N. Coalescing solar-to-chemical and carbon circular economy: mediated by metal-free porphyrin and triazine-based porous organic polymer under natural sunlight J. Mater. Chem. A , 2023 , 11 , 19183-19190.

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Coalescing solar-to-chemical and carbon circular economy: mediated by metal-free porphyrin and triazine-based porous organic polymer under natural sunlight



Authors:Saini, N.; Sharma,N.; Chauhan, D. K.; Khurana, R.; Ali, Md. E.; and Kailasam, K.

Publication Details:J. Mater. Chem. A,2023, 11, 19183-19190

Abstract:
Harnessing renewable solar energy to valorize CO2 has emerged as a promising and enduring solution to address energy and environmental challenges. However, achieving high efficiency and selectivity in the photocatalytic reduction of CO2, without relying on metals, photosensitizers, or sacrificial agents, remains a formidable hurdle. In the continuing pursuit of sustainable synthesis, in this study, we present the development of a novel metal-free photocatalyst, composed of porphyrin and a triazine-based porous organic polymeric network (TPT-porp) for the photocatalytic reduction of CO2 coupled with oxidative benzylamine homocoupling under natural sunlight for the first time. Astonishingly, we achieved an exceptional CO production rate, reaching 1786 μmol g−1 h−1, with an outstanding selectivity of >90% and selective oxidation of benzylamine, yielding N-benzylbenzaldimine with a conversion of 65% and selectivity exceeding 98% in 6 h of irradiation under natural sunlight. A remarkably high AQY of 9.34% (at λ = 430 nm) and solar-to-fuel conversion of 0.24% was attained for CO production. A series of controlled experiments, EPR studies, 13CO2 labelling experiments, and DFT studies were employed to unravel the underlying mechanism of this dual photoredox process. In summary, our pioneering study opens up unprecedented avenues for the investigation of metal-free photocatalysts capable for dual photoredox processes, and these findings offer tremendous potential for advancing the field of sustainable photocatalysis.

DOI Link: 10.1039/D3TA05160A

• Banerjee, R., Mukhe Insights into the role of the conserved GTPase domain residues T62 and S277 in yeast Dnm1 Int. J. Biol. Macromol. , 2023 , 253 , .

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Insights into the role of the conserved GTPase domain residues T62 and S277 in yeast Dnm1

Authors:Banerjee, R., Mukherjee, A., Adhikary. A., Sharma, S., Hussain, M.S., Ali, M. E., and Nagotu, S.

Publication Details:Int. J. Biol. Macromol.,2023, 253,

Abstract:


Mitochondrial division is a highly regulated process. The master regulator of this process is the multi-domain, conserved protein called Dnm1 in yeast. In this study, we systematically analyzed two residues, T62 and S277, reported to be putatively phosphorylated in the GTPase domain of the protein. These residues lie in the G2 and G5 motifs of the GTPase domain. Both residues are important for the function of the protein, as evident from in vivo and in vitro analysis of the non-phosphorylatable and phosphomimetic variants. Dnm1T62A/D and Dnm1S277A/D showed differences with respect to the protein localization and puncta dynamics in vivo, albeit both were non-functional as assessed by mitochondrial morphology and GTPase activity. Overall, the secondary structure of the protein variants was unaltered, but local conformational changes were observed. Interestingly, both Dnm1T62A/D and Dnm1S277A/D exhibited dominant-negative behavior when expressed in cells containing endogenous Dnm1. To our knowledge, we report for the first time a single residue (S277) change that does not alter the localization of Dnm1 but makes it non-functional in a dominant-negative manner. Intriguingly, the two residues analyzed in this study are present in the same domain but exhibit variable effects when mutated to alanine or aspartic acid.  

 

DOI Link: 10.1016/j.ijbiomac.2023.127381

• Kumar, P. P. P.; B Selective naked-eye detection of dopamine using an imino-boron molecular capsule New J. Chem. , 2023 , 47 , 19183-19190.

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Selective naked-eye detection of dopamine using an imino-boron molecular capsule



Authors: Kumar, P. P. P.; Bajaj, A.; Samadder, P.; Ali, Md. E.; and Neelakandan, P. P.

Publication Details:New J. Chem.,2023, 47, 19183-19190

Abstract:
Biogenic amines are responsible for transmitting electrical impulses in biological systems and hold immense physiological significance. To detect these amines under physiological conditions, optical sensing methods are favoured due to their simplicity, affordability, and rapid response. Probes based on macrocycles or molecular capsules have proven superior for chemosensing applications due to their unconventional structures and intriguing properties. Here we report the synthesis of a BF2-containing molecular capsule with high luminescence and long lifetimes in solution and in the solid state. The cylindrical cavity in the capsule encompassing polarised Bδ+–Fδ− bonds facilitates the formation of multiple hydrogen bonds with dopamine, and the complexation is signalled through visual changes in colour and fluorescence. The mechanism of interaction was studied using fluorescence and NMR spectroscopy and further supported by molecular dynamics simulations, which revealed that multiple non-covalent interactions between the molecular capsule and dopamine are responsible for stabilizing the inclusion complex. Finally, we demonstrate the use of the molecular capsule as a simple probe by preparing a test strip using a polymer for the sensing of dopamine under various conditions.

DOI Link: 10.1039/D3NJ02097E

• Khurana, R., Bajaj, High-Spin Blatter’s Triradicals J. Phys. Chem. A , 2023 , 127 , 7802–7810.

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High-Spin Blatter’s Triradicals



Authors:Khurana, R., Bajaj, A., Shamasundar, K. R., and Ali, Md. E.

Publication Details:J. Phys. Chem. A,2023, 127, 7802–7810

Abstract:
Robust organic triradicals with high-spin quartet ground states provide promising applications in molecular magnets, spintronics, etc. In this context, a triradical based on Blatter’s radical has been synthesized recently, having two low-lying non-degenerate doublet states with a quartet ground state. The traditional broken-symmetry (BS)-DFT computed doublet–quartet energy gaps are reported to be somewhat overestimated in comparison to the experimentally observed values. In this work, we have employed different ab initio methods on this prototypical system to obtain more accurate doublet–quartet energy gaps for this triradical. The spin-constraint broken-symmetry (CBS)-DFT method has been used to reduce the overestimation of energy gaps from BS-DFT. To address the issues of spin-contamination and the multireference nature of low-spin states affecting the DFT methods, we have computed the energy gaps using appropriately state-averaged CASSCF and NEVPT2 computations. Using a series of active spaces, our calculations are shown to provide quite accurate values in concordance with the experimentally observed results. Furthermore, we have proposed and modeled another two triradicals based on Blatter’s radical, which are of interest for experimental synthesis and characterization. Our computations show that all these triradicals also have a quartet ground state with a similar energy difference between the excited doublet states.  

DOI Link: 10.1021/acs.jpca.3c02683

• Mukhopadhyaya, A., S Probing the spin states of tetra-coordinated iron(II) porphyrins by their vibrational and pre K-edge x-ray absorption spectra Int. J. Quantum Chem. , 2023 , , .

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Probing the spin states of tetra-coordinated iron(II) porphyrins by their vibrational and pre K-edge x-ray absorption spectra



Authors:Mukhopadhyaya, A., Sharma, M., Oppeneer, P.M. and Ali, M.E.

Publication Details:Int. J. Quantum Chem.,2023, ,

Abstract:


Tetra-coordinated iron(II) porphyrins are observed in triplet (intermediate spin, IS) ground state with low-lying quintet (high spin, HS) and singlet (low spin, LS) excited states. It is well known in the literature that the d_Fe-N bond distances are dependent on the spin state such that the d_Fe-N distances are larger for HS compared to the LS/IS states. This implies the existence of strong magneto-structural correlations. Herein, the possibility to obtain the spin-state information for a series of tetra-coordinated square planar iron(II) porphyrin complexes have been explored by exploiting the magneto-structural correlations obtained from first principle calculations. The spin-state dependent nature of the chemical bonds and spin polarization on the N-atoms play a crucial role in the vibrational dynamics of the central Fe-atom. Theoretical nuclear resonance vibrational spectroscopy (NRVS) is adopted to investigate the vibrational dynamics and the Fe-atom associated spectral peaks and their spin-dependent features. We find that NRVS studies along with iron pre-K-edge x-ray absorption analysis convincingly provide the information on the spin state, which could be utilized to identify the spin states without adopting any magnetic probes.

 

DOI Link: 10.1002/qua.27174

• Nain, S., Kumar, M. The impact of spin-vibrational coupling on magnetic relaxation of a Co(ii) single-molecule magnet Phys. Chem. Chem. Phys. , 2023 , 25 , 14848-14861.

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The impact of spin-vibrational coupling on magnetic relaxation of a Co(ii) single-molecule magnet



Authors:Nain, S., Kumar, M. and Ali, M.E.

Publication Details:Phys. Chem. Chem. Phys.,2023, 25, 14848-14861

Abstract:
Single-molecule magnets (SMMs) based on transition metals have appeared as enticing targets exploiting magnetic anisotropy in 3d elements. Among transition metals, Co based SMMs are very prominent as they often exhibit a high spin-reversal barrier (Ueff), owing to their large unquenched orbital angular momentum. Employing the wave function-based multireference CASSCF/NEVPT2 calculations, herein we substantiate the zero-field splitting parameters of four mononuclear Co complexes and one of them has shown potential as an SMM. The mechanism of magnetic relaxation has been studied to understand the molecular origin of the slow relaxation of magnetization. The combination of suppressed quantum tunneling of magnetization (QTM) at the ground state and the high negative D value usually manifests SMM behavior in a zero-applied magnetic field. However, mere fulfillment of these conditions ensures little about their SMM behavior, as spin-vibrational coupling often plays spoilsport by lowering the spin relaxation channels. A detailed study accounting for all the 46 vibrational modes below the first-excited state for the prospective Co(II) complex, reveals one of the vibrational modes providing a lower spin relaxation pathway. This results in the development of an SMM with a Ueff value of 239.30 cm−1, decreased by ∼81 cm−1 from the value without spin-vibrational coupling.

DOI Link: 10.1039/D3CP01243C

• Neethu, K. M., Nag, A study of [2 + 2] cycloaddition–retroelectrocyclization in water: observation of substrate-driven transient-nanoreactor-induced new reactivity Org. Biomol. Chem. , 2023 , 21 , 2922-2929.

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A study of [2 + 2] cycloaddition–retroelectrocyclization in water: observation of substrate-driven transient-nanoreactor-induced new reactivity



Authors:Neethu, K. M., Nag, K., Dar, A. H., Bajaj, A., Gopal, S. A., Gowri, V., Nagpure, M. Sartaliya, S., Sharma, R., Solanki, Kumar A., Ali M. E., Muthukrishnan, Azhagumuthu, Jayamurugan, G.

Publication Details:Org. Biomol. Chem.,2023, 21, 2922-2929

Abstract:
Organic solvents limit [2 + 2] cycloaddition–retroelectrocyclization (CA–RE) in biological fields. We examined the formation of 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) through CA–RE reactions and their unusual reactivity to produce N-heterocyclic compounds when the nature of the surfactant and the concentrations were varied in the aqueous phase. An environment in which transient self-assemblies (vesicles) were induced by the substrate and surfactant molecules initiated new reactivity through H2O addition on the TCBD, generating the enol form of the intermediate, which results in the formation of the 6,6-dicyano-heteropentafulvene (amidofulvene) compound, while lamellar sheets at higher concentrations favored TCBD generation. Interestingly, the amidofulvene underwent a clean transformation to 6-membered heterocycles that resemble cardiotonic drugs (milrinone, amrinone) via keto–enol tautomerism mediated by a polar aprotic solvent, opening up a new avenue for drug discovery. Unlike organic-solvent-mediated CA–RE reactions, the present nanoreactor-mediated approach enabled the selective production of TCBDs as well as new heterocycles using H2O as a green solvent. In addition to the widely explored organic electronics/materials, we believe that this study will help to overcome the long-standing limitation of CA–RE reaction applicability in biological fields.

DOI Link: 10.1039/D3OB00053B