Dependu Dolui
@iitgn.ac.in
DST Inspire Research Fellow, Discipline of Chemistry
Indian Institute of Technology Gandhinagar
Scopus Publications
Scopus Publications
Somnath Guria, Dependu Dolui, Chandan Das, Santanu Ghorai, Vikram Vishal, Debabrata Maiti, Goutam Kumar Lahiri, and Arnab Dutta
Springer Science and Business Media LLC
AbstractFacile conversion of CO2 to commercially viable carbon feedstocks offer a unique way to adopt a net-zero carbon scenario. Synthetic CO2-reducing catalysts have rarely exhibited energy-efficient and selective CO2 conversion. Here, the carbon monoxide dehydrogenase (CODH) enzyme blueprint is imitated by a molecular copper complex coordinated by redox-active ligands. This strategy has unveiled one of the rarest examples of synthetic molecular complex-driven reversible CO2reduction/CO oxidation catalysis under regulated conditions, a hallmark of natural enzymes. The inclusion of a proton-exchanging amine groups in the periphery of the copper complex provides the leeway to modulate the biases of catalysts toward CO2 reduction and CO oxidation in organic and aqueous media. The detailed spectroelectrochemical analysis confirms the synchronous participation of copper and redox-active ligands along with the peripheral amines during this energy-efficient CO2reduction/CO oxidation. This finding can be vital in abating the carbon footprint-free in multiple industrial processes.
Abhishek Saini, Chandan Das, Surabhi Rai, Aritra Guha, Dependu Dolui, Piyali Majumder, and Arnab Dutta
Elsevier BV
Sourav Paul, Sougata Sarkar, Dependu Dolui, Debashrita Sarkar, Marc Robert, and Uttam Kumar Ghorai
Royal Society of Chemistry (RSC)
Exfoliated C3N4 sheets were employed to wrap the CoPc nanotubes (NTs) to synthesize the electrocatalyst; the CoPc–C3N4 system showed excellent nitrogen reduction to ammonia with a yield rate of 423.8 μg h−1 mgcat−1 and a FE of 33% at −0.2 V vs. RHE.
Saddam Sk, Sandip Prabhakar Shelake, Dependu Dolui, Suhana Karim, Rajib Ghosh, M. V. Jyothirmai, Annadanam V. Sesha Sainath, Ujjwal Pal, and Arnab Dutta
Royal Society of Chemistry (RSC)
Post synthetically-modified UiO-66-NH2 with a molecular cobaloxime [Co(DMG)2Cl2] (DMG = dimethylglyoxime) catalyst displays excellent photo-(404 μmol g−1 h−1) and electrocatalytic H2 evolution activity in an aqueous solution.
Ashish Kumar Yadav, Virendra Singh, Rajesh Kushwaha, Dependu Dolui, Rohit Rai, Prodyut Dhar, Arnab Dutta, Biplob Koch, and Samya Banerjee
Wiley
Four new Co(II) complexes viz., [Co(bpy)2(acac)]Cl (1), [Co(phen)2(acac)]Cl (2), [Co(bpy)2(cur)]Cl (3), [Co(phen)2(cur)]Cl (4), where bpy = 2,2'-bipyridine (1 and 3), phen = 1,10-phenanthroline (2 and 4), acac = acetylacetonate (1 and 2), cur = curcumin monoanion (3 and 4) were designed, synthesized and fully characterized. The X-ray crystal structures of 1 and 2 indicated that CoN4O2 core has a distorted octahedral geometry. The photoactivity of these complexes was tuned by varying the π conjugation in the ligands. 3 and 4 depicted an intense absorption band near 435 nm, which made them useful as visible-light PDT agents. Curcumin complexes 3 and 4 showed fluorescence with λemi = ca. 565 nm. This fluorescence was useful to study their intracellular uptake and localization in MCF-7 cancer cells. The acetylacetonate complexes (1 and 2) are used as control complexes to understand the role of curcumin. The white light-triggered anticancer profiles of the cytosol targeting complexes 3 and 4 were investigated in detail. These non-dark toxic complexes displayed significant apoptotic photo-cytotoxicity (under visible light) against MCF-7 cells via ROS generation. The control complexes 1 and 2 did not induce significant cell death in light and dark. Interestingly, 1-4 produced a remarkable antibacterial response on light exposure. Overall, the reported results here can increase the boundary of the Co(II)-based anticancer and antibacterial drug development.
Aritro Sinha Roy, Boris Dzikovski, Dependu Dolui, Olga Makhlynets, Arnab Dutta, and Madhur Srivastava
MDPI AG
The accurate analysis of continuous-wave electron spin resonance (cw ESR) spectra of biological or organic free-radicals and paramagnetic metal complexes is key to understanding their structure–function relationships and electrochemical properties. The current methods of analysis based on simulations often fail to extract the spectral information accurately. In addition, such analyses are highly sensitive to spectral resolution and artifacts, users’ defined input parameters and spectral complexity. We introduce a simulation-independent spectral analysis approach that enables broader application of ESR. We use a wavelet packet transform-based method for extracting g values and hyperfine (A) constants directly from cw ESR spectra. We show that our method overcomes the challenges associated with simulation-based methods for analyzing poorly/partially resolved and unresolved spectra, which is common in most cases. The accuracy and consistency of the method are demonstrated on a series of experimental spectra of organic radicals and copper–nitrogen complexes. We showed that for a two-component system, the method identifies their individual spectral features even at a relative concentration of 5% for the minor component.
Rajesh Kushwaha, Virendra Singh, Silda Peters, Ashish K. Yadav, Dependu Dolui, Sukanta Saha, Sujit Sarkar, Arnab Dutta, Biplob Koch, Tumpa Sadhukhan,et al.
American Chemical Society (ACS)
Photodynamic therapy (PDT) has evolved as a new therapeutic modality for cancer treatment with fewer side effects and drug resistance. Curcumin exhibits PDT activity, but its low bioavailability restricts its clinical application. Here, the bioavailability of curcumin was increased by its complex formation with the Zn(II) center. For a structure-activity relationship study, Zn(II)-based complexes (1-3) comprising N^N-based ligands (2,2'-bipyridine in 1 and 2 or 1,10-phenanthroline in 3) and O^O-based ligands (acetylacetone in 1, monoanionic curcumin in 2 and 3) were synthesized and thoroughly characterized. The X-ray structure of the control complex, 1, indicated a square pyramidal shape of the molecules. Photophysical and TD-DFT studies indicated the potential of 2 and 3 as good visible light type-II photosensitizers for PDT. Guided by the TD-DFT studies, the low-energy visible light-triggered singlet oxygen (1O2) generation efficacy of 2 and 3 was explored in solution and in cancer cells. As predicted by the TD-DFT calculations, these complexes produced 1O2 efficiently in the cytosol of MCF-7 cancer cells and ultimately displayed excellent apoptotic anticancer activity in the presence of light. Moreover, the molecular docking investigation showed that complexes 2 and 3 have very good binding affinities with caspase-9 and p-53 proteins and could activate them for cellular apoptosis. Further molecular dynamics simulations confirmed the stability of 3 in the caspase-9 protein binding site.
Ab Qayoom Mir, Sukanta Saha, Sampurna Mitra, Somnath Guria, Piyali Majumder, Dependu Dolui, and Arnab Dutta
Royal Society of Chemistry (RSC)
Electrocatalytic and photocatalytic H2 production from water with a vitamer appended synthetic catalyst.
Dependu Dolui, Ab Qayoom Mir, and Arnab Dutta
Royal Society of Chemistry (RSC)
The photo- and electrocatalytic H2 production by the cobaloxime core improves in the presence of a primary amine group in the periphery.
Dependu Dolui, Santanu Ghorai, and Arnab Dutta
Elsevier BV
Abstract The construction of an efficient, inexpensive, and durable H2 production electrocatalyst is considered as an indispensable tool for the inception of a hydrogen-mediated alternative energy technology. Recently, cobalt-based molecular complexes have emerged as one of the realistic candidates for this key role of H2 evolution catalyst due to their intrinsic oxygen tolerance and moderately efficient proton reduction ability. However, the issues pertaining to the water solubility and long-term stability of those cobalt complexes have limited their practical applications. Recently, several research groups have adopted an enzyme-inspired catalyst design strategy, where variable basic functionalities were appended around the existing core-cobalt complexes to improve their water solubility. Additionally, presence of these peripheral groups enhances catalytic H2 evolution activity of the modified complexes by boosting the proton transduction around the framework. Inclusion of this biomimetic outer coordination sphere feature also induced structural flexibility around the metal core to improve the stability of the complexes under demanding catalytic conditions. In this article, we have specifically portrayed the multi-dimensional regulatory roles effectuated by these fluxional basic functionalities during the catalytic H2 production by the cobalt-based molecular complexes.
Dependu Dolui, Shikha Khandelwal, Piyali Majumder, and Arnab Dutta
Royal Society of Chemistry (RSC)
The rational inclusion of enzyme-inspired features around the cobaloxime core reinstates its status as a leading synthetic photo-/electro-catalyst for hydrogen production.
Pooja Shukla, Soumalya Roy, Dependu Dolui, Walter Cañón-Mancisidor, and Sourav Das
Wiley
Dependu Dolui, Srewashi Das, Jaya Bharti, Shivam Kumar, Pankaj Kumar, and Arnab Dutta
Elsevier BV
Summary Hetero-axial cobalt complexes are known for their oxygen-tolerant photocatalytic hydrogen production activity, mostly in organic solvents. Here, variable combinations of peripheral basic groups are explicitly positioned around an existing complex framework to generate an enzyme-inspired minimal outer coordination sphere (OCS) scaffold. This catalyst design strategy yields a series of water-soluble, upgraded versions of imidazole-linked cobaloximes. The presence of fringe protic functionalities ensures the formation of a dynamic and water-mediated proton relay. This appended proton relay allows us to probe imidazole-bound cobaloxime in pure aqueous conditions. It exhibits highly efficient electrocatalytic (TOF ∼4,900 s−1) and photocatalytic (TON ∼12,000) hydrogen production in neutral water compared to its relatively moderate performance in organic media. The catalyst retains its activity (TON ∼22), even under natural sunlight (sunny day in Gandhinagar) in aerobic aqueous solution, emphasizing the importance of OCS features for producing robust, natural-condition-ready, synthetic catalysts.
Dependu Dolui, Shikha Khandelwal, Althaf Shaik, Deepika Gaat, Vijay Thiruvenkatam, and Arnab Dutta
American Chemical Society (ACS)
Construction of a water-soluble, oxygen-tolerant, and acid-stable synthetic H2 production catalyst is vital for the development of an economic and user-friendly H2-based renewable energy infrastructure. Natural enzyme hydrogenases exhibit excellent energy-efficient H2 production activity. However, fragility of the overall protein structure has restricted their sustainable and practical application. Among the synthetic functional models of hydrogenase, cobaloxime-based complexes offer O2-insensitivity. However, they are only active near neutral conditions with moderate rates and poor aqueous solubility properties. Here, in this work, we have specifically stationed a series of enzyme-inspired, multicomponent outer coordination sphere components around the cobaloxime core to simultaneously improve its catalytic rate, aqueous solubility, and activity even under acidic conditions. We have also established that cobaloximes display catalytic H2 production via two independent mechanisms: (i) Co(II)-centric and (i...
Ab Qayoom Mir, Dependu Dolui, Shikha Khandelwal, Harshil Bhatt, Beena Kumari, Sanmitra Barman, Sriram Kanvah, and Arnab Dutta
MyJove Corporation
Developing photocatalytic H2 production devices is the one of the key steps for constructing a global H2-based renewable energy infrastructure. A number of photoactive assemblies have emerged where a photosensitizer and cobaloxime-based H2 production catalysts work in tandem to convert light energy into the H-H chemical bonds. However, the long-term instability of these assemblies and the need for hazardous proton sources have limited their usage. Here, in this work, we have integrated a stilbene-based organic dye into the periphery of a cobaloxime core via a distinct axial pyridine linkage. This strategy allowed us to develop a photosensitizer-catalyst hybrid structure with the same molecular framework. In this article, we have explained the detailed procedure of the synthesis of this hybrid molecule in addition to its comprehensive chemical characterization. The structural and optical studies have exhibited an intense electronic interaction between the cobaloxime core and the organic photosensitizer. The cobaloxime was active for H2 production even in the presence of water as the proton source. Here, we have developed a simple airtight system connected with an online H2 detector for the investigation of the photocatalytic activity by this hybrid complex. This photosensitizer-catalyst dyad present in the experimental setup continuously produced H2 once it was exposed in the natural sunlight. This photocatalytic H2 production by the hybrid complex was observed in aqueous/organic mixture media in the presence of a sacrificial electron donor under complete aerobic conditions. Thus, this photocatalysis measurement system along with the photosensitizer-catalyst dyad provide valuable insight for the development of next generation photocatalytic H2 production devices.
Shikha Khandelwal, Afridi Zamader, Vivek Nagayach, Dependu Dolui, Ab Qayoom Mir, and Arnab Dutta
American Chemical Society (ACS)
The protein scaffold plays a key role during the enzymatic catalysis for metalloenzymes. Here we have rationally designed an enzyme-inspired outer coordination sphere in the form of protic functionalities, such as natural amino acid derived carboxylic acid and phenolic −OH groups, on the fringe of the cobalt-salen like complexes. This inclusion has enabled electrocatalytic H2 evolution for an otherwise inactive cobalt-salen like core. The complexes containing peripheral carboxylic acid groups exhibited unique pH-switchable catalytic H2 production that is connected with the pKa of the carboxylic acid group (∼4.0), suggesting the crucial involvement of the carboxylate group during the catalytic activity. The one- and two-dimensional NMR results of the complexes have indicated the presence of a possible hydrogen bonding network, generated by those protic groups in aqueous solution. These results highlight that an inactive metal complex can be activated for specific small molecule activation via rational incl...