Enriching NLO efficacy via designing non-fullerene molecules with the modification of acceptor moieties into ICIF2F: an emerging theoretical approach

Computational method on highly efficient D-π-A-π-D-based different molecular acceptors for organic solar cells applications and non-linear optical behaviour

Eight molecular structures (BT-A1 to BT-A8) with high-performance non-fullerene acceptor (NFA) were selected for organic solar cells (OSCs) and non-linear optical (NLO) applications. Their electronic, photovoltaic (PV) and optoelectronic properties were tuned by adding powerful electron-withdrawing groups to the acceptor (A) of the D-π-A-π-D structure. Using time-dependent density functional theory (TD-DFT) techniques, based on the laws of quantum chemical calculations, the absorption spectra, stability of the highest and lowest-energy molecular orbitals (HOMO/LUMOs), electron density, intramolecular charge transfer (ICT), transition density matrix (TDM), were examined. The binding energy (Eb) and density of states (DOS) were probed to realize the optoelectronic analysis of the structures BT-A1 to BT-A8. Noncovalent interactions (NCIs) based on a reduced density gradient (RDG) were used to describe the nature and strength of D-A interactions in the molecules BT-A1 to BT-A8. The new refined molecules BT-A1 to BT-A8 exhibited strong absorbance bands between 408-721 nm and high electron transfer contribution (ETC) ranges between 87-96 %, along with the smallest excitation energies (Ex) between 1.71-3.55 eV in the solvent dichloromethane. Dipolar moment strengths ranging from 0.38 to 4.72 Debye in both the excited and ground states have determined with good solubility properties of BT-A1 to BT-A8 in polar solvent. Highly effective charge mobilities and prevention of charge recombination have been demonstrated by the electron (0.18-0.41 eV) and hole RE values (0.13-0.89 eV) for the new compounds. Power conversion efficiencies (PCE) of BT-A1 to BT-A8 were nearly the same because of better outcomes compared to the molecules in the BT. Compared to poly[4.8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b: 4,5-b']dithiophene-2,6- diyl-alt-(4-2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th), the open circuit voltages (Voc) of compounds BT-A1 to BT-A8 were ranged from 1.52 to 2.13 eV. The polarizability (α) and hyperpolarizability (β) of the molecules BT-A1 to BT-A8 were used to determine the non-linear optical (NLO) properties. The results showed that BT-A2, BT-A6 and BT-A7 have good NLO activity. This computational analysis demonstrates the superiority of the molecules with NFA. Hence the compounds are advised for the use in production of high-performance OSCs and NLO activity.

Electronic and Nonlinear Optical Properties of B(III)-Submonoazaporphyrin-π-Diimide Compounds: A Density Functional Theory Study

Three hypothetical complexes were designed using diimides (PMDI, NTCDI, and PTCDI) as the acceptor unit and B(III)-submonoazaporphyrin (1) as the donor unit. These complexes have smaller HOMO-LUMO energy gaps (3.39-3.96 eV) than pristine 1 (6.61 eV). Further, the energy gap can be tuned by changing the number of benzene rings of these diimides. Remarkably, these proposed complexes possess considerable first hyperpolarizabilities (β0) (4865-6921 a.u.), and the regularity of the β0 values remained the same in the gas phase and toluene solvent conditions. There is an inverse relationship between the energy gap and the polarizability/first hyperpolarizability. In addition, absorption spectra, frontier molecular orbitals, and hole electron distributions were obtained using time-dependent density functional theory calculations to emphasize the relationship between structure and properties. Ultraviolet-Visible absorption spectra reveals that all complexes show satisfying IR working regions. Further analysis of the first hyperpolarizability density reveals the nature of the excellent NLO properties of the studied systems. This study can provide valuable insights for the development of potential high-performance NLO molecules.

Star-shaped small donor molecules based on benzotriindole for efficient organic solar cells: a DFT study

CONTEXT

The purpose of the S01-S05 series of end-capped modified donor chromophores is to amplify the energy conversion efficiency of organic solar cells. Using quantum chemical modeling, the photophysical and photoelectric characteristics of the S01-S05 geometries are examined.

METHOD

The influence of side chain replacement on multiple parameters, including the density of states (DOS), molecular orbital analysis (FMOS), exciton-binding energy (Eb), molecular electrostatic potential analysis, dipole moment (μ), and photovoltaic characteristics including open circuit voltage (VOC), and PCE at minimal energy state geometries, has been investigated employing density functional theory along with TD-DFT analysis. The molar absorption coefficient (λmax) of all the proposed compounds (S01-S05) was efficiently enhanced by the terminal acceptor alteration technique, as demonstrated by their scaling up with the reference molecule (SR). Among all molecules, S04 has shown better absorption properties with a red shift in absorption having λmax at 845 nm in CHCl3 solvent and narrow energy gap (EG) 1.83 eV with least excitation energy (Ex) of 1.4657 eV. All created donors exhibited improved FF and VOC than the SR, which significantly raised PCE and revealed their great efficiency as OSC. Consequently, the results recommended these star-shaped molecules as easily attainable candidates for constructing extremely efficient OSCs.

Exploration of nonlinear optical properties of 4-methyl-4H-1,2,4-triazol-3-yl)thio)-N-phenylpropanamide based derivatives: experimental and DFT approach

Triazoles, nitrogen-containing heterocycles, have gained attention for their applications in medicinal chemistry, drug discovery, agrochemicals, and material sciences. In the current study, we synthesized novel derivatives of N-substituted 2-((5-(3-bromophenyl)-4-methyl-4H-1,2,4-triazol-3-yl)thio)-N-phenylpropanamide and conducted a comprehensive investigation using density functional theory (DFT). These novel structural hybrids of 1,2,4-triazole were synthesized through the multi-step chemical modifications of 3-bromobenzoic acid (1). Initially, compound 1 was converted into its methyl-3-bromobenzoate (2) which was then transformed into 3-bromobenzohydrazide (3). The final step involved the cyclization of compound 3, producing its 1,2,4-triazole derivative (4). This intermediate was then coupled with different electrophiles, resulting in the formation of the final derivatives (7a-7c). Additionally, the characterization of these triazole-based compounds (7a, 7b, and 7c) were carried out using techniques such as IR, HNMR, and UV-visible spectroscopy to understand their structural and spectroscopic properties. The DFT study utilized M06/6-311G(d,p) functional to investigate geometrical parameters, HOMO-LUMO energies, natural bond orbital analyses, transition density matrix (TDM), density of states, and nonlinear optical (NLO) properties. The FMO analysis revealed that compound 7c exhibited the lowest band gap value (4.618 eV). Notably, compound 7c exhibited significant linear polarizability (4.195 >  × 10-23) and first and second hyperpolarizabilities (6.317 >  × 10-30, 4.314 × 10-35), signifying its potential for nonlinear optical applications. These NLO characteristics imply that each of our compounds, especially 7c, plays a crucial part in fabricating materials showing promising NLO properties for optoelectronic applications.

Heterocyclic Donor Moiety Effect on Optical Nonlinearity Behavior of Chrysene-Based Chromophores with Push-Pull Configuration via the Quantum Chemical Approach

Organic-based nonlinear optical (NLO) materials may be used in many optical-electronic systems and other next-generation defense technologies. With the importance of NLO materials, a series of push-pull architecture (D-π-A) derivatives (DTMD2-DTMD6) were devised from DTMR1 through structural alteration of different efficient donor heterocyclic groups. Density functional theory-based computations were executed at the MPW1PW91/6-31G(d,p) level to explore the NLO behavior of the derivatives. To investigate the optoelectronic behavior of the said compounds, various analyses like the frontier molecular orbital (FMO), global reactivity parameters, density of state (DOS), absorption spectra (UV-vis), natural bond orbital, and transition density matrix (TDM) were performed. The derivatives have a smaller band gap (2.156-1.492 eV) and a larger bathochromic shift (λmax = 692.838-969.605 nm) as compared to the reference chromophore (ΔE = 2.306 eV and λmax = 677.949 nm). FMO analysis revealed substantial charge conduction out of the donor toward the acceptor via a spacer that was also shown by TDM and DOS analyses. All derivatives showed promising NLO results, with the maximum amplitude of linear polarizability ⟨α⟩ and first (βtotal) and second (γtotal) hyperpolarizabilities over their reference chromophore. DTMD2 contained the highest βtotal (7.220 × 10-27 esu) and γtotal (1.720 × 10-31 esu) values corresponding with the reduced band gap (1.492 eV), representing potential futures for a large NLO amplitude. This structural modification through the use of various donors has played a significant part in achieving promising NLO behavior in the modified compounds.

Influence of acceptors on the optical nonlinearity of 5H-4-oxa-1,6,9-trithia-cyclopenta[b]-as-indacene-based chromophores with a push-pull assembly: a DFT approach

Herein, a series of compounds (TPD1-TPD6) having a D-π-A architecture was quantum chemically designed via the structural modulation of TPR. Quantum chemical calculations were employed to gain a comprehensive insight into the structural and optoelectronic properties of the designed molecules at the M06/6-311G(d,p) level. Interestingly, all the designed chromophores displayed narrow energy gaps (2.123-1.788 eV) and wider absorption spectra (λmax = 833.619-719.709 nm) with a bathochromic shift in comparison to the reference compound (λmax = 749.602 nm and Egap = 3.177 eV). Further, Egap values were utilized to evaluate global reactivity parameters (GRPs), which indicate that all the chromophores expressed higher softness (σ = 0.134-0.559 eV-1) and lower hardness (η = 4.155-4.543 eV) values than the reference chromophore. Efficient charge transfer from donors towards acceptors was noted through FMOs, which was also supported by DOS and TDM analyses. Overall, the TPD3 derivative exhibited a remarkable reduction in the HOMO-LUMO band gap (1.788 eV) with a red shift as λmax = 833.619 nm. Furthermore, it exhibited prominent linear and non-linear characteristics such as μtotal = 24.1731 D, 〈α〉 = 2.89 × 10-22 esu, and βtotal = 7.24 × 10-27 esu, among all derivatives. The above findings revealed that significant non-linear optical materials could be achieved through structural tailoring with studied efficient acceptors.

Linear and Nonlinear Optical Responses of Nitrobenzofurazan-Sulfide Derivatives: DFT-QTAIM Investigation on Twisted Intramolecular Charge Transfer

In this study, we report on the green fluorescence exhibited by nitrobenzofurazan-sulfide derivatives (NBD-Si, i = 1-4). The optical responses of these studied compounds in a polar methanol solvent were simulated by the use of time-dependent density functional theory (TD-DFT) employing the Becke-3-Parameter-Lee-Yang-Parr (B3LYP) functional along with the 6-31G(d,p) basis set. The computed energy and oscillator strength (f) results complement the experimental results. The band gap was calculated as the difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Additionally, the density of states (DOS) was computed, providing a comprehensive understanding of the fundamental properties of these materials and further corroborating the experimental data. When the experimental data derived from ultraviolet/visible (UV/visible) and fluorescence spectroscopic techniques and those from simulated spectra are analyzed, the extracted values match up adequately. In addition, the NBD-sulfide compounds exhibit a large Stokes shift up to 85 nm in a polar methanol solvent. They are hypothesized to represent a novel paradigm of excited-state intramolecular charge transfer (ICT). To understand the intrinsic optical properties of NBD-Si materials, an ICT was identified, and its direction within the molecule was evaluated using the ratio of βvect and βtotal, values extracted from the computed nonlinear optical (NLO) properties. Moreover, the reduced density gradient (RDG)-based noncovalent interactions (NCIs) were employed to characterize the strength and type of NBD-Si interactions. Furthermore, noncovalent interactions were identified and categorized using the Quantum Theory of Atoms in Molecules (QTAIM) analysis. Ultimately, the combination of Hirshfeld surface analysis and DFT calculations was utilized to enhance the characterization and rationalization of these NCIs.

Facile Synthesis and DFT Analysis of Novel Thiazole-Based Hydrazones: An Experimental and Theoretical Perspective

Hydrazone compounds with remarkable nonlinear optical (NLO) properties were found with vast applications due to their cost-effective synthesis and greater stability. Therefore, we synthesized hydrazone scaffolds (TCAH1-TCAH8) by condensation reaction, and their structural confirmation was accomplished with spectroscopic methods (1H-, 13C-NMR, and HRMS). Quantum chemical calculations were also performed at B3PW91/6-311G(d,p) functional of DFT to explore electronic, structural, and chemical properties. To understand the NLO responses of afore-said chromophores, various kinds of analyses such as natural bonding orbitals (NBOs), frontier molecular orbitals (FMOs), UV-vis analysis, and density of states (DOS) were performed. Findings showed that the HOMO-LUMO energy gap in TCAH8 (3.595 eV) was found to be lower than the TCAH1-TCAH7 (4.123-3.932 eV) with a large red shift which leads to a substantial NLO response. Furthermore, strong intramolecular interactions showed the highest stabilization energy (24.1 kcal mol-1) for TCAH8 in the NBO transitions, combined with the least binding energy. The significant NLO response of TCAH4 was explored with ⟨α⟩, βtot, and ⟨γ⟩ values as 5.157 × 10-23, and 2.185 × 10-29, and 2.753 × 10-34 esu, respectively, among the entitled compounds. The recent findings may inspire scientists to develop extremely effective NLO materials for forthcoming hi-tech applications.

Green synthesis of heterocyclic alkenes using MCM 41 supported perchloric acid catalytic system: characterization and DFT studies

CONTEXT

In this work, a series of heterocyclic alkenes were prepared by the reaction of 2-hydroxy-1-naphthaldehyde with various heterocyclic active methylene compounds via Knoevenagel condensation reaction using mesoporous silica, MCM 41, supported perchloric acid as an efficient green catalytic system under solvent-free conditions. A comparative study of the conventional method vs the green method was also reported with the same raw materials. ¹H NMR, ¹³C NMR, IR, and mass spectroscopic techniques were used for the characterization of synthesized compounds.

METHODS

Computational study was performed for these compounds by applying density functional theory (DFT) at M06 functional and 6-311G (d,p) basis set to interpret the electronic structures and counter check the experimental findings. The frequency analysis with aforementioned levels of DFT was performed to confirm the stability associated with optimized geometries. The true minimum for the optimized geometries for 1, 2, and 3 was achieved as indicated by the absence of negative eigenvalues in all the calculated frequencies. Additionally, natural bond orbitals (NBOs) and nonlinear optical (NLO) properties were explored utilizing the aforementioned level and basis set combination via DFT, whereas the frontier molecular orbitals (FMOs) evaluation was done at time-dependent density functional theory TDDFT at M06/6-311G(d,p). The global reactivity parameters were also calculated using the FMO data. These computation-based outcomes were found in good agreement with the experimental findings.

Synthesis of novel 3-hydroxy-2-naphthoic hydrazones as selective chemosensors for cyanide ions

The development of an effective and selective chemosensor for CN^- ions has become the need of the hour due to their hazardous impact on the environment and humans. Herein, we report the synthesis of two novel chemosensors, IF-1 and IF-2 based on 3-hydroxy-2-naphthohydrazide and aldehyde derivatives that have shown selective sensing of CN^- ions. IF-2 exhibited exclusive binding with CN^- ions that is further confirmed by the binding constant value of 4.77 × 10⁴ M^-1 with a low detection limit (8.2 μM). The chemosensory potential is attributed to deprotonation of the labile Schiff base center by CN^- ions that results in a color change from colorless to yellow as visible by the naked eye. Accompanying this, a DFT study was also performed in order to find the interaction between the sensor (IF-1) and its ions (F^-). A notable charge transfer from 3-hydroxy-2-naphthamide to 2,4-di-tert-butyl-6-methylphenol, was indicated by the FMO analysis. The QTAIM analysis revealed that in the complex compound, the strongest pure hydrogen-hydrogen bonding was observed between H53 and H58, indicated by a ρ value of +0.017807. Due to its selective response, IF-2 can be successfully used for making test strips for the detection of CN^- ions.

Study of the Crystal Architecture, Optoelectronic Characteristics, and Nonlinear Optical Properties of 4-Amino Antipyrine Schiff Bases

Two Schiff bases, (E)-4-((2-chlorobenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (4AAPOCB) and (E)-4-((4-chlorobenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (4AAPPCB), have been synthesized and grown as single crystals. Single-crystal X-ray diffraction analysis was employed to determine the crystal structure of the compounds, and the results suggest that the compounds crystallized into an orthorhombic crystal system having P2₁2₁2₁ and Pbca space groups, respectively. Further, the crystallinity of the compounds was analyzed by the PXRD technique. The UV-vis-NIR spectra of the compounds demonstrate excellent transmittance in the entire visible region. The lower cutoff wavelengths of the compounds were determined to be 338 and 333 nm, respectively; additionally, optical band gaps of the compounds found were 4.60 and 4.35 eV. FTIR and NMR (¹H and ¹³C) spectral techniques were utilized to analyze the molecular structure of the compounds. The compounds emit photoluminescence with broad emission bands with centers at 401 and 418 nm. The thermal stability and phase transitions were assessed through thermogravimetric methods. The phase transition prior to melting was indicated by the endothermic event at around 190 °C in the DTA curves of both crystals, and the same was observed in the DSC curves. The second harmonic efficiencies of the powdered compounds I and II were found to be 3.52 and 1.13 times better than that of the standard reference KDP. The 4AAPOCB and 4AAPPCB compounds showed isotropic polarizability amplitudes of 46.02 × 10^-24 and 46.52 × 10^-24 esu, respectively. The calculation of linear polarizability and NLO second-order polarizability (β) along with other optical parameters was performed for optimized geometries. The nonzero amplitudes of the average β values for compounds 4AAPOCB and 4AAPPCB were found to be 14.74 × 10^-30 and 8.10 × 10^-30 esu, respectively, which show a decent potential of the synthesized molecules for NLO applications. The calculated β amplitudes were further explained based on calculated electronic parameters like molecular electrostatic potentials, frontier molecular orbitals, molecular orbital energies, transition energies, oscillator strengths, and unit spherical representation of NLO polarizability. The current analysis emphasizes the significance of synthesized compounds as prospective candidates for optical and NLO applications through the use of experiments and quantum computations.

Effect of different end-capped donor moieties on non-fullerenes based non-covalently fused-ring derivatives for achieving high-performance NLO properties

A series of derivatives (DOCD2-DOCD6) with D-π-A configuration was designed by substituting various efficient donor moieties via the structural tailoring of o-DOC6-2F. Quantum-chemical approaches were used to analyze the optoelectronic properties of the designed chromophores. Particularly, M06/6-311G(d,p) functional was employed to investigate the non-linear optical (NLO) response (linear polarizability ⟨α⟩, first (β_tot) and second ([Formula: see text]_tot) order hyperpolarizabilities) of the designed derivatives. A variety of analyses such as frontier molecular orbital (FMO), absorption spectra, transition density matrix (TDMs), density of states (DOS), natural bond orbital (NBO) and global reactivity parameters (GRPs) were employed to explore the optoelectronic response of aforementioned chromophores. FMO investigation revealed that DOCD2 showed the least energy gap (1.657 eV) among all the compounds with an excellent transference of charge towards the acceptor from the donor. Further, DOS pictographs and TDMs heat maps also supported FMO results, corroborating the presence of charge separation states along with efficient charge transitions. NBO analysis showed that π-linker and donors possessed positive charges while acceptors retained negative charges confirming the D-π-A architecture of the studied compounds. The λ_max values of designed chromophores (659.070-717.875 nm) were found to have broader spectra. The GRPs were also examined utilizing energy band gaps of E_HOMO and E_LUMO for the entitled compounds. Among all the derivatives, DOCD2 showed the highest values of β_tot (7.184 × 10^-27 esu) and [Formula: see text]_tot (1.676 × 10^-31 esu), in coherence with the reduced band gap (1.657 eV), indicating future potentiality for NLO materials.

First theoretical framework for highly efficient photovoltaic parameters by structural modification with benzothiophene-incorporated acceptors in dithiophene based chromophores

Now a days, researchers are constantly doing efforts to upgrade the performance of solar based devices with the aim of increasing the role of photovoltaic materials in modern hi-tech optoelectronic applications. Realizing the recent energy conditions across the globe, research is diverted from fullerene to non-fullerene electron acceptor moieties in this era, considering their remarkable contribution in organic solar cells (OSCs). Therefore, we designed seven novel non-fullerene fused ring electron acceptor chromophores (MD2–MD8) from DOC2C6-2F by structural tailoring with different acceptors at end-capped units. DFT study was performed at B3LYP functional to discover the opto-electronic characteristics of the newly tailored chromophores. Various analysis such as frontier molecular orbitals (FMOs), transition density matrix (TDM), density of states (DOS), binding energy (Eb), reorganization energy, open circuit voltage (Voc) was carried out to comprehend the photovoltaic response of MD2–MD8. Decrease in band gaps (1.940–1.571 eV) with wider absorption spectrum (725.690–939.844 nm in chloroform) along with greater charge transfer rate from HOMO towards LUMO were examined in derivatives as compared to MR1 (Egap = 1.976 eV, λmax = 738.221 nm) except MD7. Further, in all derivatives, smaller values of Eb (0.252–0.279 eV) were examined than that of reference (0.296 eV). These lower binding energy values of MD2–MD8 indicated the higher rate of excitation dissociation with lager charger transfer rate than MR1, which further supported by DOS and TDM analyses. Additionally, least reorganization energy in the aforesaid compounds for hole with electron was also inspected. Moreover, Voc a good photovoltaic response was noted for all studied compounds which indicated that these compounds are suitable to synthesize OSCs in future.

Exploration of the interesting photovoltaic behavior of the fused benzothiophene dioxide moiety as a core donor with modification in acceptors for high-efficacy organic solar cells

Non-fullerene-based chromophores with end-capped acceptor modification used in organic solar cells (OSCs) have proven to offer improved performance. Therefore, eight unique benzothiophene-based molecules (D2-D9) were designed by the end-capped acceptor manipulation of a reference molecule (R1). Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations at the B3LYP level were performed to investigate various parameters such as the optical properties, frontier molecular orbitals (FMOs), transition density matrix (TDM), binding energy, density of states (DOS), open-circuit voltage (V _oc), and reorganization energies of electrons (λ _e) and holes (λ _h), to better understand the optoelectronic properties of the newly designed compounds. All the derivatives had broader absorption spectra of 737.562-700.555 nm with a reduced energy gap of 2.132-1.851 eV compared to those of the reference (719.082 nm), except for D8 and D9. A comparable value of V _oc and lower reorganization energies were found in the derivatives compared to those of R1. Within the studied compounds, D3 was predicted to be a good optoelectronic material for environmentally friendly organic solar cells (EFOSCs) because of its superior optoelectronic capabilities, low-energy band gap (1.851 eV), highest λ _max values of 794.516 and 744.784 nm in chloroform and the gas phase, respectively, and lowest transition energy (1.561 eV) than those of the reference and the other derivatives. Subsequently, end-capped acceptor modification was proven to be an effective method to achieve desired optoelectronic characteristics.

Synthesis, Characterization, and DFT-Based Electronic and Nonlinear Optical Properties of Methyl 1-(arylsulfonyl)-2-aryl-1H-benzo[d]imidazole-6-carboxylates

Herein, a series of N-1-sulfonyl substituted derivatives of 2-substituted benzimidazoles (2a-2e) were designed and synthesized via structural tailoring of the acceptor part of donor-π-acceptor schemes, and their nonlinear optic (NLO) characteristics were reported. The structures of 2a-2e were investigated and their characterization was accomplished by employing spectroscopic procedures, i.e., UV-vis, FT-IR, and ¹H and ¹³C NMR. Further, a density functional theory (DFT) approach was used to calculate UV-vis, vibrational, and ¹H and ¹³C NMR techniques; frontier molecular orbitals (FMOs); global reactivity parameters (GRPs); natural bond orbitals (NBOs); optical and vibrational analysis; and nonlinear optics (NLO). The most promising results were obtained for 6-nitro-2-(4-nitrophenyl)-1-(4-nitrophenylsulfonyl)-1H-benzo[d]imidazole among entitled compounds, as it exhibited the highest ⟨α⟩ and β_tot values, showing it is an eye-catching NLO material. This DFT study evokes the interest of researchers regarding the development of benzimidazole-based tempting NLO compounds that could be beneficial in modern hi-tech applications.

Synthesis, nonlinear optical analysis and DFT studies of D–π–D and A–π–A configured Schiff bases derived from bis-phenylenediamine

Electronic and structural parameters of four synthesized (DMA, DMM, DAM, and DMD) and one designed (DMB-D) Schiff bases have been explored.