Category Archives: Journal of Physical Organic Chemistry

A computational study of double perovskites A2BI6 (A = Cs, K, Rb; B = Pt, Sn) invoking density functional theory

Posted on 17 May 2023 by nBobby Solanki, nPooja Sharma, nPrabhat Ranjan, nPancham Kumar, nTanmoy Chakrabortyn

Perovskite materials K₂PtI₆, K₂SnI₆, and Rb₂SnI₆ can be potential candidates for photovoltaic cells. System Cs₂SnI₆ shows maximum stability among the studied compounds. K₂PtI₆ with the least value of HOMO-LUMO energy gap displays maximum value of the refractive index and dielectric constant.

Abstract

Lead-free double perovskite materials A₂BI₆ (A = Cs, K, Rb; B = Pt and Sn) have been studied and analyzed invoking density functional theory (DFT). Computed values of the HOMO–LUMO gap for lead-free double perovskites material A₂BI₆ are found in the range of 1.062–2.811 eV. The energy gaps of K₂PtI₆, K₂SnI₆, and Rb₂SnI₆ are in the optimal energy gap range (0.9 to 1.6 eV) required for a lead-free double perovskite system. Conceptual DFT-based descriptors, viz., molecular hardness, softness, electronegativity, electrophilicity index, dipole moment, and polarizability, are computed. The result reveals that K₂PtI₆ shows high efficacy towards electron injection and may show the maximum electron driving force. The optical properties—refractive index and dielectric constant—of these perovskites are also computed. The maximum value of refractive index and dielectric constant is found for K₂PtI₆. Our computed results are in good agreement with the available experimental and other theoretical data. Perovskite materials K₂PtI₆, K₂SnI₆, and Rb₂SnI₆ display a suitable energy gap as well as a high refractive index and dielectric constant, which makes them suitable for photovoltaic applications.

Electronic and optical properties of lead‐free double perovskites A2BCl6 (A = Rb, Cs; B = Si, Ge, Sn) for solar cell applications: A systematic computational study

Posted on 13 February 2023 by n Saloni, nPancham Kumar, nPooja Sharma, nPrabhat Ranjan, nTanmoy Chakrabortyn

In this report, we have studied lead-free perovskite materials A₂BCl₆ (A = Rb, Cs; B = Si, Ge, Sn) using the DFT technique. DFT-based global descriptors of perovskite materials are computed and analyzed. Our results reveal that Rb₂SiCl₆ is the most suitable material among the studied compounds for solar cell applications. Other parameters, namely, tolerance factor, optical properties, and IR and Raman spectra of A₂BCl₆, are also reported.

Abstract

In recent years, lead-free double perovskite materials have attracted much attention due to their probable applications in photovoltaic and optoelectronic devices. In this work, the electronic and optical properties of lead-free double perovskites A₂BCl₆ (A = Rb, Cs; B = Si, Ge, and Sn) are studied using density functional theory (DFT) methodology. The result shows that the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps of these compounds vary between 0.524 and 0.919 eV, which agrees with the previously reported data. HOMO-LUMO gap for Rb₂SiCl₆ is observed as 0.919 eV, which falls in the optimal energy gap range, that is, 0.9 to 1.6 eV for double perovskite material. Conceptual DFT-based descriptors—molecular hardness, softness, electronegativity, electrophilicity index, and dipole moment of these compounds—are studied. The tolerance factor of A₂BCl₆ is observed in the range of 1.00 to 1.26. Rb₂SnCl₆ is almost a perfect fit with a value of 1.00. Cs₂SiCl₆ shows the maximum value of the refractive index and dielectric constant. Optical electronegativity is found between 0.178 and 0.246 eV. The suitable band gap and high value of the refractive index and dielectric constant make double perovskites A₂BCl₆ effective for solar cells and optoelectronic devices.

Incorporation of graphene oxide to metal‐free phthalocyanine through hydrogen bonding for optoelectronic applications: An experimental and computational study

Posted on 10 February 2023 by

Graphene oxide was attached to imidazole substituted metal-free phthalocyanine at low processing times. The optoelectronic properties were studied experimentally and theoretically. The results suggest improved nonlinear optical properties although the conjugation was accomplished with hydrogen bonding without covalent attachment.

Abstract

This paper focuses on incorporation of graphene oxide (GO) to metal-free phthalocyanine (MPc) through only hydrogen bonding and π-π stacking. Briefly, Pc-GO composites at various concentrations were prepared by self-assembly method. The processing time was kept below 10 min to avoid covalent attachment and we aimed at answering the research question of what will happen if the conjugation is realized only through hydrogen bonding under extremely limited processing times. The as-prepared MPc-GO composites were characterized by Fourier transform infrared (FT-IR), UV-Vis, scanning electron microscope (SEM), and fluorescence analysis. We report that the interaction between MPc and GO could immediately be initiated upon mixing of corresponding solutions. Also, complete conjugation by hydrogen bonding and π-π stacking could be reached even only in 5 min of sonication time. In addition, it was also determined that the prepared MPc-GO composites are stable at room conditions and during dilution. Finally, the optoelectronic properties of MPc and MPc-GO composites were also investigated experimentally and theoretically. Both experimental and theoretical results suggest that MPc-GO composites exhibit improved optoelectronic properties as compared to MPc, even though the conjugation of GO to MPc was only via hydrogen bonding without covalent attachment.

Structure, bonding, and interaction with molecular hydrogen of the β‐D‐glucopyranose―silver+ (1:1) complex

Posted on 26 October 2022 by nSukanta Mondaln

In silico study discloses the nature of bonding in β-D-glucopyranose – silver ion (1:1) complex ([Ag(C6H12O6)]+). The metal center can interact with up to three hydrogen molecules with a binding energy of 5.3 kcal/mol per H₂.

Abstract

In silico studies have been carried out at PBE0-D3/def2-TZVP level of theory to disclose the nature of bonding in β-D-glucopyranose – silver ion (1:1) complex ([Ag(C₆H₁₂O₆)]⁺). Moreover, the interaction of molecular hydrogen with the [Ag(C₆H₁₂O₆)]⁺ complex is studied. In doing so, it is found that the metal site can interact with up to three hydrogen molecules with a binding energy of 5.3 kcal/mol per H₂. Calculated ∆G _{298 K} values disclose that the interaction of the first H₂ with the [Ag(C₆H₁₂O₆)]⁺ complex is exergonic, whereas a slightly endergonic nature of interaction is noted for the two and three H₂ cases. Electron density and electron density-based reactivity descriptors help in resolving the nature of interaction between metal ions and C₆H₁₂O₆ as well as between the metal center and molecular hydrogens. An energy decomposition analysis reveals the orbital interaction as the major contributing factor to the total interaction energy for the one H₂ case. Ab initio molecular dynamics study at different temperatures reveals kinetic stability of the hydrogen-bound silver complex up to 1 ps. Conceptual density functional theory (CDFT) based reactivity descriptors, hardness and electrophilicity, help in assessing the stability trend of the hydrogen-bound complexes during the simulation.

Biological activity of some thiazolyl‐thiadiazines as BACE‐1 inhibitors for Alzheimer’s disease in the light of density functional theory based quantum descriptors

Posted on 17 October 2022 by

Electron affinity, total electronic energy and electron transfer as promising descriptors for estimation of biological activity of thiazolyl-thiadiazines (BACE-1 inhibitors).

Abstract

This paper presents first report on a systematic investigation on developing quantum chemical descriptors on understanding biological activity (pIC₅₀) of a series of 10 thiazolyl-thiadiazines (ID-01 to ID-10) as Beta site amyloid precursor protein cleaving enzyme 1 (BACE-1) protein inhibitors for Alzheimer diseases, under density functional theory. The interactions between inhibitors and model biomolecule are studied in terms of charge and energy transfer, where the target biomolecule at the host BACE-1 protein is identified from the family of 20 amino acids, which are universal to all living organisms. The present study identifies electron affinity (EA), total electronic energy (E), and the electron transfer with amino acid (∆E) of thiazolyl-thiadiazines as promising descriptors, which can explain about 90% of observed biological activity. The developed regression model for training set is also validated for unknown test set of homologous compounds. The developed quantum chemical descriptors for prediction of the biological activity of thiazolyl-thiadiazines will certainly be an excellent addition in the QSAR parlance of drug development.

Density functional and graph theory computations of vibrational, electronic, and topological properties of porous nanographenes

Posted on 26 September 2022 by nKrishnan Balasubramaniann

Density functional and graph theoretical techniques are employed to compute the electronic, vibrational, and topological properties of porous nanographenes built from kekulene, septulene, extended kekulenes, circumkekulene, and circumseptulene.

Abstract

We have utilized the density functional theory (DFT) in conjunction with graph-theoretical techniques to compute the vibrational, electronic and topological properties of porous nanographenes starting with the building blocks of kekulene, septulene, extended kekulenes, and circumkekulene. Furthermore, graph theoretically based spectral polynomials and other topological properties including Kekulé counts, delocalization energies, and resonance energies are computed for such structures and larger tessellations of kekulenes which are precursors to nanographene belts with multiple pores. The success of the DFT methods is demonstrated with the computed vibrational modes and infrared and Raman spectra of several of these structures. The computed spectral polynomials and the spectra reveal the underlying patterns of the energy levels and structural features and hence suggest the possibility of integration of graph theory with quantum chemical techniques for the computations of properties of large porous graphenes including the possibility of the Pariser–Parr–Pople (PPP) method with parameters extracted from machine learning of the DFT computations on a combinatorial library of precursors. Finally, the computations reveal that the porous structures can be tailored for sequestration of various ions including heavy metal ions for environmental remediation.

Designing of PC31BM‐based acceptors for dye‐sensitized solar cell

Posted on 3 August 2022 by nDebolina Paul, nUtpal Sarkarn

Dye with fullerene C₃₀ and C₁₀B₁₀N₁₀ as acceptor is good for DSSC.

Abstract

Three push-pull dyes with triphenylamine as donor, thiophene as spacer and fullerene-based acceptors have been designed using density functional theory (DFT) for dye-sensitized solar cells (DSSCs). Here, we have done a systematic case study by varying the acceptor of dye. PCBM type of acceptors are chosen. However, the main focus lies on the fact that fullerene C₆₀, which is used as conventional fullerene in PCBM, is replaced by C₃₀. Further, two more structures are derived, where C₃₀ is changed by two of its doped counterparts, C₁₀B₁₀N₁₀ and C₁₀B₁₀P₁₀. Structural integrity of these dyes is checked and found to be stable. Their electronic properties also provide a good insight into their characteristics. Highest occupied molecular orbital (HOMO) energy level of the dyes is positioned under the redox potential of redox couple, I3−/I−$$ {\mathrm{I}}_3^{-}/{\mathrm{I}}^{-} $$, which means that the dyes can be regenerated. LUMO energy value of dyes with C₃₀ and C₁₀B₁₀N₁₀ lies above the conduction band of semiconductor, TiO₂, and hence electrons from the excited state of the dyes can be injected into the conduction band edge of TiO₂. For C₁₀B₁₀P₁₀, lowest unoccupied molecular orbital (LUMO) lies slightly below the conduction band of TiO₂ (for B3LYP functional). Therefore, few more configurations of C₁₀B₁₀P₁₀ have been checked by replacing B and P atoms with C atoms. Notably, incorporation of solvent rules out this exception and all the dyes become eligible for electron regeneration also. Time-dependent DFT (TDDFT) studies throw light on their photochemical properties, which is one of the interim criteria for any system getting selected as a dye in the DSSCs.

Investigation of intramolecular hydrogen bonding in naphthoquinone derivatives by quantum chemical calculations

Posted on 22 July 2022 by nAnjali Sharma, nVinay Kumar Verma, nJyoti Bala Singh, nMridula Guinn

Interplay of aromatic energy and hydrogen bonding energy in stabilizing naphthoquinone conformers was shown; overall stability is dictated by the aromatic stabilization instead of hydrogen bonding energy. Maximum hardness principle and minimum electrophilicity principle supports the stability of naphthoquinone conformers. The total energy partition analysis describes electrostatic interaction as the major force in stabilizing these systems.

Abstract

Intramolecular hydrogen-bonded naphthoquinone derivatives are investigated using both DFT (density functional theory) and MP2 (Møller–Plesset perturbation theory) method. Three different sets of naphthoquinone derivatives, each set consisting of syn and anti conformers with respect to the substitution by (–OH/–NH₂) at peri and para position of the ring, are considered for investigation. In all cases, the syn conformer is found to be energetically more stable compared with the anti conformer. However, the hydrogen bond strength of the anti conformer is found to be more as obtained from NBO (natural bond orbital) analysis and QTAIM (quantum theory of atoms in molecules) theory. The O···H–O interactions are associated with covalent character while O···H–N interactions are noncovalent in nature. The NCI (noncovalent interaction) isosurface clearly indicates the formation of O···H–O and O···H–N intramolecular hydrogen bond. The energy partition analysis indicates electrostatic interaction as the dominant force in stabilizing these systems. The aromaticity calculation by HOMA (harmonic oscillator model of aromaticity) index and Bird index indicate the syn conformer with higher aromaticity compared to the anti conformer. The overall stability of the syn conformers is thus dominated by the aromatic stabilization energy instead of hydrogen bonding energy. The global reactivity descriptors further support the higher stability of the syn conformers according to maximum hardness principle (MHP) and minimum electrophilicity principle (MEP).

Electronegativity: A continuing enigma

Posted on 1 July 2022 by nPeter Politzer, nJane S. Murrayn

Equating electronegativity to the negative of the chemical potential is neither valid nor useful, as this definition leads to results that are incompatible with chemical experience. A more effective approach, which gives results in overall agreement with Pauling's values, is to relate electronegativity to the average valence electron ionization energies of atoms.

Abstract

There continues to be confusion concerning the concept of electronegativity. Pauling's original approach, focusing upon an atom in a molecule, continues to be widely invoked. There has also been a more recent tendency to view electronegativity as the negative of the chemical potential and to extend it to molecules. However, this leads to results that are incompatible with chemical experience. A more effective approach, which gives results in overall agreement with Pauling's values, is to relate electronegativity to the average valence electron ionization energies of atoms.

Removal of erythrosine B dye from wastewater using chitosan boric acid composite material: Experimental and density functional theory findings

Posted on 30 June 2022 by

In this study, the chitosan boric acid (Ch-B) composite has been prepared and characterized with sophisticated analytical techniques such as FT-IR, SEM and EDX. The prepared Ch-B adsorbent was applied for the adsorption of erythrosine B (EB) dye from water samples under the optimized parameters of pH, adsorbent dosage, time and temperature. Results shows that the Ch-B adsorbent remove 96.5% of EB dye at pH 5, using 0.05 g of adsorbent.

Abstract

In this study, the chitosan boric acid (Ch-B) composite has been prepared and characterized with sophisticated analytical techniques such as FT-IR, SEM, and EDX. The prepared Ch-B adsorbent was applied for the adsorption of erythrosine B (EB) dye from water samples under the optimized parameters of pH, adsorbent dosage, time, and temperature. Results shows that the Ch-B adsorbent removes 96.5% of EB dye at pH 5, using 0.05 g of adsorbent. The adsorption equilibrium data have been subject to the Langmuir, Freundlich, and D-R adsorption equilibrium models, which demonstrates that the Freundlich model was the best fit with good correlation coefficient value (R ² = 0.991), while energy E (9.18 KJ·mol⁻¹) calculated from D-R model suggested that the physical adsorption nature of the adsorption. Beside this, the thermodynamic and kinetic experiments were performed to check the feasibility and adsorption mechanism of EB-dye onto Ch-B adsorbent, which shows that the adsorption is endothermic (∆H = 0.124) and spontaneous in nature due to the negative values of Gibbs free energy (i.e., ∆G KJ·mol⁻¹ = −13.01, −17.06, and −17.60). The kinetic models show that the adsorption equilibrium is best fitted with pseudo second order kinetic model due to good correlation coefficient (R ² = 0.99). Moreover, the interaction phenomenon between adsorbent and adsorbate was analyzed through DFT calculations.