Publications
2021 Onwards
Anchor Group Effects in Ruthenium(II) Photosensitizers Bearing N-Heterocyclic Carbene and Polypyridyl Ligands for DSSCs: A Computational Evaluation. Angelina Mary, Abbas Raja Naziruddin*. New J. Chem. 2024, 48, 17564-17573
(DOI: 10.1039/D4NJ03729D)
In this work, we evaluate the bonding characteristics and interfacial electron transfer dynamics of three heteroleptic ruthenium photosensitizers featuring different terpyridine (tpy) acceptor end configurations through quantum-chemical calculations. These photosensitizers feature tpy ligands with a mono/tricarboxylic acid or a phenyl-carboxylic acid anchor and a trans-disposed –NCS and N-heterocyclic carbene ligand in a C^N donor set. Adiabatic transitions reveal significant overlap between higher-excited and ground-state orbitals and correlate with the experimentally observed anti-Kasha fluorescence. In all complexes, two carboxylate-O atoms of the central anchor effectively bind with TiO2 by bridging two titanium sites. However, appending an additional anchor on each peripheral pyridine of tpy renders binding through only one anchor's –C=O atom to TiO2. Contrary to the complex bearing three anchors, those featuring monocarboxylate-functionalized tpy exhibit faster electron injection within 100 fs. In all, this study provides insights into the photosensitization attributes of the ruthenium complexes for dye-sensitized solar cells.
Terpyridine Based Heteroleptic Ruthenium Complexes: Influence of Donor and Acceptor Ligands in Photosensitization. Nimisha Jain, Angelina Mary, Tanu Singh, Srushti Gadiyaram, Jyoti Joshi, D. Amilan Jose, Abbas Raja Naziruddin*. Eur. J. Inorg. Chem. 2023, 26, e202300210
(DOI: 10.1002/ejic.202300210)
We report heteroleptic ruthenium complexes of terpyridine (tpy) ligands with directly linked carboxylic acid anchors. These complexes feature methyl or methoxy-substituted 4'-Phtpy as donor ligands. We prepared these heteroleptic complexes from the ruthenium (II) precursor via a milder route to preclude the homoleptic complex formation. The donor–acceptor arrangement of tpy ligands in these ruthenium complexes renders visible light absorption giving metal and ligand-to-ligand charge transfer excitations at c.a. 490 nm. We evaluate the effect of the tpy donor substituents on the light harvesting ability in Dye-Sensitized Solar Cells (DSSCs) and compare their photosensitizing ability with heteroleptic complexes bearing phenyl spacer at the acceptor end. Further, scrutinizing their photovoltaic performance, we studied their electron transfer kinetics in DSSCs using electrochemical impedance spectroscopy. This paper presents the structure-photosensitization relationship of these heteroleptic ruthenium complexes through a combined experimental and computational approach.
Heteroleptic Ruthenium(II) Complexes Featuring N-Heterocyclic Carbene-Based C^N Donor Sets for Solar Energy Conversion. Nimisha Jain, Angelina Mary, Tanu Singh, Srushti Gadiyaram, D. Amilan Jose, Abbas Raja Naziruddin*. New J. Chem. 2023, 47, 13476-13485
(DOI: 10.1039/D3NJ01432K)
We present a series of heteroleptic ruthenium(II) complexes featuring N-heterocyclic carbene-based C^N donor sets functionalized with long hydrophobic chains ( decyl and octyl) and -NCS ligands. These complexes utilize mono or tricarboxy terpyridine (tpy) ligands as anchors to bind with TiO2 photoanodes. Herein, the synthetic route preferably gave access to only the complexes with NHC and -NCS ligands in trans-orientation. Complexes exhibit a wider visible-light absorptivity tailing till 750 nm. Stronger electron donation from C^N donor set and an -NCS ligand propel these metal-ligand-to-ligand charge transfer excitations, transferring the electron density toward the carboxylate anchors. We evaluate the performance of these NHC-based ruthenium complexes in a typical dye-sensitized solar cell setup. The electrochemical and photophysical attributes of complexes underline their ability to convert solar energy into electricity. Further, interfacial electron transport parameters obtained from electrochemical impedance spectroscopy give deeper insight into the performance of devices. We also present our analyses from electronic-structure calculations to support the experimental results.
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Sunlight-assisted photocatalytic degradation of azo-dye using zinc-sulfide embedded reduced graphene oxide. Chumki Dalal, Anjali Kumari Garg, Nimisha Jain, Abbas Raja Naziruddin, Rajneesh Kumar Prajapati, Shyam Kumar Choudhary*, Sumit Kumar Sonkar*. Sol. Energy. 2023, 251, 315–324
(DOI: 10.1016/j.solener.2023.01.017)
Herein, Zinc sulfide embedded reduced graphene oxide nanocomposites (ZnS-rGO) have been prepared using a simple precipitation method. The as-prepared ZnS-rGO has been applied for sunlight-promoted selective degradation of Congo Red (CR), an azo dye in a short time and even when combined with spiking industrial wastewater. The ZnS-rGO shows ~98% degradation of CR dye with a rate constant of 0.0266 min−1 by following pseudo-first-order kinetics. Sunlight as a sustainable energy source produces the best results (~three times higher) than experiments done in artificial bulb light, during photocatalytic degradation of similar concentrations of CR dye. The effect of dye concentration and loading of catalyst on photocatalytic degradation efficiency has also been explored. The role of reactive oxygen species responsible for photocatalytic degradation is examined by employing trap experiments, confirms the significant contribution of superoxide radicals. Additionally, ZnS-rGO is able to degrade CR dye in a broad pH range and used to degrade CR from industrially spiked wastewater samples to demonstrate the photocatalyst's potential for their use in the real-world applications. Moreover, comparative NMR and FTIR analysis support the photocatalytic degradation of CR dye.
Magnetic Graphene Nanosheets from Expired Iron-Supplemented Tablets for Hydroxyl-Mediated Photocatalytic Oxidation of Azo Dyes. Deepika Saini, Simran Dumra, Vishrant Kumar, Ruchi Aggarwal, Abbas Raja Naziruddin, Sumit Kumar Sonkar*. ACS Appl. Nano Mater. 2023, 6, 3, 1573-1581
(DOI: 10.1021/acsanm.2c04313)
In the present report, we employed a single-step simpler pyrolytic process for synthesizing magnetic graphene nanosheets (m-GNS) using expired iron-supplemented tablets. The microscopic morphological results showed the formation of multilayered graphene nanosheets (m-GNS) doped with iron oxide nanoparticles that impart magnetic behavior. m-GNS are used here as advanced oxidative materials to break down an azo dye named acid orange 7 (AO7). In the presence of sunlight, the rate of photodegradation of the AO7 dye is seven times faster than that under artificial light (visible and infrared), which significantly advocates the influence of sunlight. Based on trapping experiments, the production of hydroxyl radicals under sunlight has majorly been responsible for the photodegradation of the AO7 dye. A comparative nuclear magnetic resonance analysis was performed to support the breaking down of the complex organic framework of AO7 dyes into low-molecular-weight hydrocarbons.
Regulation of Nitric Oxide (NO) Release by Membrane Fluidity in Ruthenium Nitrosyl Complex-Embedded Phospholipid Vesicles. Nancy Sharma, D. Amilan Jose*, Nimisha Jain, Shubhangi Parmar, Anupama Srivastav, Jaya Chawla, Abbas Raja Naziruddin, C. R. Mariappan. Langmuir. 2022, 38, 44, 13602–13612
(DOI: 10.1021/acs.langmuir.2c02457)
Incorporating water-insoluble nitric oxide (NO)-releasing molecules into biocompatible vesicles may allow for the tunable control of NO release on a specific target site. In vesicles, membrane fluidity plays an important role and influences the final therapeutic efficiency of drugs loaded into the vesicles. Hence, we aimed to investigate the effect of lipid fluidity on the NO release behavior of the photo-controllable ruthenium nitrosyl (Ru-NO) complex. In this regard, a new photoactive ruthenium nitrosyl complex (L.Ru-NO) with amphiphilic terpyridine ligand was synthesized and characterized in detail. L.Ru-NO was incorporated with commercial phospholipids to form nanoscale vesicles L.Ru-NO@Lip. The photoactive {Ru-NO}6 type complex released NO in the organic solvent CH3CN and aqueous liposome solution by irradiating under low-intensity blue light (λ = 410 nm, 3 W). To demonstrate the effect of lipid structure and fluidity on NO release, four different liposome systems L.Ru-NO@Lip1–4 were prepared by using phospholipids such as DOPC, DSPC, DPPC, and DMPC having different chain lengths and saturation. The NO-releasing abilities of these liposomes in aqueous medium were studied by UV–vis spectrum, colorimetric Greiss, and fluorescent DAF assay. The results show that the rate of NO release could be easily tuned by varying the lipid fluidity. The effect of temperature and pH on NO release was also studied. Further, the complex L.Ru-NO and liposomes L.Ru-NO@Lip1 were assayed as an antibacterial agent against the strains of bacteria Escherichia coli and Staphylococcus aureus.
Ruthenium Complexes Bearing Bis-N-Heterocyclic Carbene Donors in TiO2 Sensitization for Dye-Sensitized Solar Cells. Nimisha Jain, Angelina Mary, Pooja Munish Dalal, Rahul Sakla, D. Amilan Jose, Mukesh Jain, Abbas Raja Naziruddin*. Eur. J. Inorg. Chem. 2022, e202200705
(DOI: 10.1002/ejic.202200705).
Ruthenium (II) complexes bearing N-Heterocyclic carbenes-based C^C donors and terpyridine monocarboxylic acid (tpy4'-COOH) are prepared. π-spacers are also introduced between tpy and -COOH groups. Isonicotinic acid or thiocyanate ligands completed the octahedral coordination sphere. DSSCs are fabricated using these complexes, and their photovoltaic performances are evaluated.
Ruthenium (II) Complexes Bearing N-Heterocyclic Carbene Based C^N Donor Sets in Dye-Sensitized Solar Cells. Angelina Mary, Nimisha Jain, Rahul Sakla, D. Amilan Jose, Bhagwan Sahai Yadav, Abbas Raja Naziruddin*. Appl. Organomet. Chem. 2022, e6873
(DOI: 10.1002/aoc.6873).
This paper presents the preparation of ruthenium photosensitizers from N-Heterocyclic carbenes (NHC) based C^N donor set, NCS, and mono-carboxylic acid-functionalized terpyridine ligands. With only one coordinating NCS ligand, we achieve a wider visible light absorptivity, giving 3.44% photon conversion efficiency (PCE).
Photo Controlled Release of Nitric Oxide (NO) from Amphiphilic and Nanoscale Vesicles Based Ruthenium Nitrosyl Complex: NO release and Cytotoxicity Studies. Nancy Sharma, Porkizhi Arjunan, Srujan Marepally, Nimisha Jain, Abbas Raja Naziruddin, Amrita Ghosh, C.R. Mariappan, D. Amilan Jose*, J. Photochem. Photobiol. A: Chem. 2022, 425, 113703
(DOI: 10.1016/j.jphotochem.2021.113703).
Amphiphilic 1.Ru-NO incorporated nanoscale vesicles (Lip-1.Ru-NO) are bio-compatible and 100% water soluble. The liposome Lip-1.Ru-NO gradually releases NO both in UV and blue light, with relatively high efficiency as compared to 1.Ru-NO in CH3CN and CH3CN-water mixture. Lip-1.Ru-NO are not toxic to the cells before and after NO release.
Ruthenium Complexes Bearing N-Heterocyclic Carbene Based CNC and CN^CH2C’ Pincer Ligands: Photophysics, Electrochemistry and Solar Energy Conversion. Nimisha Jain, Angelina Mary, Vishesh Manjunath, Rahul Sakla, Rupesh S Devan, D. Amilan Jose, Abbas Raja Naziruddin*, J. Organomet. Chem. 2022, 959, 122203
(DOI: 10.1016/j.jorganchem.2021.122203).
[Ru(CNC/CN^CH2C′)(tpy4′-Ph-COOH)](PF6)2 featuring the N-heterocyclic carbene based CNC/CN^CH2C′ type pincer ligands and carboxyphenyl terpyridine are reported. The enhancement of lifetime is in line with the computed-near octahedral bite angle of 89° for the CN^CH2C′ pincer-ligand at the ruthenium center. The σ-donating and π-back bonding abilities of NHC donors are also studied.
Ruthenium (II) Complexes Bearing Heteroleptic Terpyridine Ligands: Syntheses, Photophysics and Solar Energy Conversion. Nimisha Jain, Angelina Mary, Vishesh Manjunath, Rahul Sakla, Rupesh S Devan, D. Amilan Jose, Abbas Raja Naziruddin*, Eur. J. Inorg. Chem. 2021​, 2021, 5014-5023
(DOI: 10.1002/ejic.202100817).
Milder reaction conditions give ruthenium (II) complexes bearing donor and acceptor functionalized terpyridine ligands. The nature of electronic states is studied by spectroscopic methods, electrochemistry and supported by dispersion-corrected density functional theory calculations. We herein evaluate the solar energy conversion of these thiocyanate-free complexes in dye-sensitized solar cells.
