Sandeep B. Mane

Novel expanded porphyrin sensitized solar cells using boryl oxasmaragdyrin as the sensitizer

Oxasmaragdyrin boron complexes were prepared and applied in DSSCs. The HOMO-LUMO energy gap analyses and theoretical calculations revealed that these expanded porphyrins are ideal sensitizers for DSSCs. A device containing oxasmaragdyrin-BF2 as the sensitizer achieves an energy conversion efficiency of 5.7%.

Effects of Number and Position of Meta and Para Carboxyphenyl Groups of Zinc Porphyrins in Dye-Sensitized Solar Cells: Structure–Performance Relationship

Porphyrin sensitizers containing meta- and para-carboxyphenyl groups in their meso positions have been synthesized and investigated for their performance in dye-sensitized solar cells (DSSCs). The superior performance of para-derivative compared to meta-derivative porphyrins was revealed by optical spectroscopy, electrochemical property measurements, density functional theory (DFT) calculations, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, incident photon-to-current conversion efficiency (IPCE), electrochemical impedance spectroscopy (EIS), and stability performance. Absorption spectra of para-carboxyphenyl-substituted porphyrins on TiO2 show a broader Soret band compared to meta-carboxyphenyl-substituted porphyrins. ATR-FTIR spectra of the studied porphyrins on TiO2 were applied to investigate the number and mode of carboxyl groups attached to TiO2. The VOC, JSC, and IPCE values of para-series porphyrins were distinctly superior to those of meta-series porphyrins. The Nyquist plots of the studied porphyrins show that charge injection in para-series porphyrins is superior to that in meta-series porphyrins. The orthogonally positioned para derivatives have more efficient charge injection and charge transfer over charge recombination, whereas the efficiencies of flat-oriented meta derivatives are retarded by rapid charge recombination. Photovoltaic measurements of the studied meta- and para-carboxyphenyl-functionalized porphyrins show that the number and position of carboxyphenyl groups play a crucial role in the performance of the DSSC. Our results indicate that para-carboxyphenyl derivatives outperform meta-carboxyphenyl derivatives to give better device performance. This study will serve as a guideline for the design and development of organic, porphyrin, and ruthenium dyes in DSSCs.

Synthesis of carboxylate functionalized A3B and A2B2 thiaporphyrins and their application in dye-sensitized solar cells

A series of novel A3B and A2B2 thiaporphyrins consisting of mono or dual anchoring groups with different linkers has been synthesized and effectively applied in dye-sensitized solar cells (DSSCs). The presence of an ethynylphenyl linker has a pronounced effect on their optical, electrochemical and photovoltaic properties. The ethynylphenyl linker bathochromically shifted the absorption spectra. Density functional theory (DFT) studies revealed that attachment of an ethynylphenyl linker through one of the meso positions to the porphyrin core results in planar macrocycles which is essential for the active electron coupling of the porphyrin core with the anchoring group in DSSCs. Although the dual anchoring groups can bind strongly to the TiO2 surface, the presence of the ethynylphenyl linker and especially the electron withdrawing cyano group on the anchoring group proved to be the pivotal factors to achieve higher efficiency. Among these dyes, N3S-ECN, having an ethynylphenyl linker and a cyano acrylic acid as the anchor, achieved the highest efficiency of 1.69%, with Jsc = 5.12 mA cm−2, Voc = 0.49 V and ff = 67%. To the best of our knowledge this is the highest efficiency obtained for thiaporphyrins.

Molecular Engineering of Boryl Oxasmaragdyrins through Peripheral Modification: Structure–Efficiency Relationship

Expanded porphyrins with the absorption profile down to the infrared region through increased π-conjugation are suitable candidates for a low energy sensitizer. Oxasmaragdyrin boron complexes, a class of aromatic-core-modified expanded porphyrin with 22 π-electrons, have been recently utilized as an efficient low energy sensitizer in dye-sensitized solar cells. In this paper, we have prepared a series of eight novel boryl oxasmaragdyrins through molecular engineering on the periphery and their overall photovoltaic performances in dye-sensitized solar cells are evaluated. With the help of photophysical, electrochemical, and photovoltaic studies, it is revealed that molecular structure, especially the number and position of the donor-acceptor groups play a pivotal role in their photovoltaic performance. Presence of the two well-separated split Soret bands in the 400-500 nm region of UV/Vis spectrum ensures broader coverage of absorption wavelengths. Even though the two-anchoring-group dyes (SM5-SM8) bind strongly to TiO2 compared to one-anchoring-group dyes (SM1-SM4), the latter have superior photovoltaic performance than the former. Dye SM1, with two hexyloxyphenyl donors and one carboxylic acid anchor showed the best overall conversion efficiency of 4.36% (JSC = 10.91 mA cm(-2); VOC = 0.59 V; FF = 0.68). This effective modulation of photovoltaic performance through structural engineering of the dyes will serve as a guideline for the future design of efficient low energy light-harvesting sensitizers.

A Ni(II) dinuclear complex bridged by end-on azide-N and phenolate-O atoms: spectral interpretation, magnetism and biological study

A potential tetradentate monoanionic N2O2 chelator, HL, derived from the condensation of o-vanillin and N,N-dimethylethylenediammine, has been reacted with nickel perchlorate and sodium azide to yield the dinuclear Ni(II) complex [Ni(L)(μ1,1-N3)Ni(L)(OH2)2]·ClO4 (1), where L = Me2N(CH2)2NCH–C6H3(O−)(OCH3). The complex has been characterized by X-ray diffraction analysis and different spectroscopic techniques. The coordination geometry around the Ni(II) centres is a distorted octahedron, with the azide ligand and the phenolato oxygen atom bridging in μ1,1 and μ2 mode, respectively. The EPR spectra, recorded at liquid nitrogen temperature (77 K) and room temperature (298 K), show g factors of 2.080 and 2.085, in agreement with the structure determined by X-ray diffraction analysis. The VTM study confirms that there are ferromagnetic interactions between the bridging binuclear Ni(II) ions (S = 1). The evaluation of cytotoxic effects on different human cancer cell lines (A-549, MCF-7 and CaCo-2) suggests that both the ligand and complex 1 have potential anticancer properties. Furthermore, they also exhibit anti-mycobacterial activity against M. tuberculosis H37Rv (ATCC 27294) and M. tuberculosis H37Ra (ATCC 25177) strains. Molecular docking of HL with the enoyl acyl carrier protein reductase of M. tuberculosis H37Rv (PDB ID: 4U0K) has been examined, showing that HL forms two hydrogen bonds with Lys165 (1.94 and 2.53 A) in its best docked pose.

Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells

The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH3NH3PbI3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (Voc = 1.09 V, Jsc = 20.9 mA cm-2, fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (Voc = 1.07 V, Jsc = 22.9 mA cm-2, FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH3NH3PbI3.

A rare doubly nitrato and phenoxido bridged trimetallic CuII complex: EPR, antiferromagnetic coupling and theoretical rationalization

A rare trimetallic CuII complex, [Cu3(L)2(NO3)2] (1) has been afforded incorporating a [CuL] metalloligand, [where H2L = N,N′-bis(salicylidene)-1,3-propanediamine]. In 1, in addition to the double phenoxido bridge, the two terminal CuII atoms are linked to the central CuII by means of syn–anti bridging nitrate anions giving rise to a linear arrangement. Complex 1 exhibits strong antiferromagnetic coupling and shows an χMT value of 0.703 cm3 mol−1 K at 300 K. DFT computational studies reveal that there is a clear magneto-structural correlation between the Cu–O–Cu angle and the JCu–Cu values, which is in accordance with the experimental evidence. The biological effect of 1 on the viability of different human carcinoma cells was evaluated using MTT assay and the results indicate that this complex induces a decrease in cell-population growth of human colorectal carcinoma cells (COLO 205) with apoptosis.

Co-sensitization of free-base and zinc porphyrins: An effective approach to improve the photon-to-current conversion efficiency of dye-sensitized solar cells

Co-sensitization of two or more sensitizers with complementary absorption profiles had been utilized as an imperative tool to achieve panchromatic sensitization in dye-sensitized solar cells. The highly efficient dye-sensitized solar cells consist of a co-sensitization system comprising of a mixture of porphyrin and organic dye. We have prepared four novel free-base and zinc porphyrins in minimum steps and examined their individual as well as co-sensitized performance in dye-sensitized solar cells. The UV-visible spectrum suggests that upon zinc insertion the absorption wavelength is red-shifted by 10 nm in both Soret and Q-band region. The density functional theory (DFT) calculations revealed that the presence of an electron withdrawing cyanoacrylic acid as the anchoring group has pronounced effect on the charge distribution. IPCE spectra suggest that the co-sensitization of a free-base porphyrin with a zinc porphyrin resulted in panchromatic absorption in whole visible region. The device made with Mix-2, which is composed from the free-base porphyrin N4CN and the zinc porphyrin N4ZnCN gave the best performance with an overall photon-to-current conversion efficiency of 4.18%, with Jsc of 10.4 mA.cm-2, Voc of 0.56 V and fill factor of 72%.

Doubly end-on azido bridged mixed-valence cobalt trinuclear complex: spectral study, VTM, inhibitory effect and antimycobacterial activity on human carcinoma and tuberculosis cells

Doubly end-on azido-bridged mixed-valence trinuclear cobalt complex, [Co3(L)2(N3)6(CH3OH)2] (1) is afforded by employing a potential monoanionic tetradentate-N2O2 Schiff base precursor (2-[{[2-(dimethylamino)ethyl]imino}methyl]-6-methoxyphenol; HL). Single crystal X-ray structure reveals that in 1, the adjacent Co(II) and Co(III) ions are linked by double end-on azido bridges and thus the full molecule is generated by the site symmetry of a crystallographic twofold rotation axis. Complex 1 is subjected on different spectral analysis such as IR, UV-vis, emission and EPR spectroscopy. On variable temperature magnetic study, we observe that during cooling, the χMT values decrease smoothly until 15K and then reaches to the value 1.56 cm(3) K mol(-1) at 2 K. Complex 1 inhibits the cell growth on human lung carcinoma (A549 cells), human colorectal (COLO 205 and HT-29 cells), and human heptacellular (PLC5 cells) carcinoma cells. Complex 1 exhibits anti-mycobacterial activity and considerable efficacy on Mycobacterium tuberculosis H37Rv ATCC 27294 and H37Ra ATCC 25177 strains.

A new Cu(II) three-dimensional network with 4,4′-oxybis benzoic acid: structural diversity, EPR, and magnetism

The copper derivative {[Cu4(oba)4(H2O)4]∙H2O}n (1) has been hydro(solvo)thermally synthesized by combining flexible 4,4′-oxybis benzoic acid (oba) and divalent copper nitrate. As a result of the potential coordination modes of carboxylate oxygens from the oba ligand, the aforementioned complex leads to the formation of an interesting 3D framework, as evidenced by single-crystal X-ray diffractometry. Concerning the topology in 1, the dimers [Cu2C4O8] are nodes of a 5-fold 4-connected uninodal net of the type lvt, with point symbol {42.84} and vertex symbol [4.4.84.84.88.88]. The encapsulation of the copper coordination polymer displays a moderate luminescent property. On temperature-dependent magnetic study, it reveals that the magnetic behaviour of 1 can be associated to a strong antiferromagnetic coupling between the two Cu(II) ions.