Ground-state intermolecular donor–acceptor complex (MCPNTf
2
-MN; 1:1) is formed between
π
-electron of 1-methyl-naphthalene (MN) as solute (electron-rich) and
π
+
electron of ...1-methyl-4-cyanopyridinium bis((trifluoromethyl)sulfonyl)amide (MCPNTf
2
) as solvent (electron deficient), observed in solid state. Intermolecular charge-transfer (IMCT) band is observed, indicating the formation of stable MCPNTf
2
-MN complex. The IMCT process of MCPNTf
2
-MN complex depends on relative strength of
π
–
π
+
stack between cation of MCPNTf
2
IL and aromatic unit of MN. From DFT studies, it is clear that the geometry and interactions in MCPNTf
2
-MN complex are also influenced by NTf
2
anion. This solute–solvent interaction shows the deviation of inertness nature of MCPNTf
2
IL. AIM analysis, electron localization function (ELF) and localized orbital locator (LOL) surface maps are obtained to achieve information regarding intermolecular interactions in the complex. Hirshfeld surface analysis and its fingerprint maps are used to identify pairwise interactions between atoms in order to avail molecular packing of the complexes from crystallographic data. NCI plots display combination of specific atom–atom interactions through hydrogen bond and vdW interactions. AIMD study shows that the complex attains a lower energy of − 2630.72 hartree at 125 and 445 fs.
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•Intramolecular aliphatic (CH··O) H-bonding in piperidinium based ILs is reported.•H-bonding helps in keeping piperidinium cation and DNP anion together.•DSC, TGA, SCXRD and ...vibrational spectroscopic techniques are employed.•NBO, AIM, ELF, LOL, NCI theoretical analysis are also performed.•ab initio molecular dynamics is used to study H-bonding interactions in ILs.
Hydrogen bonding interaction plays an important role in the stability of the building blocks of various materials. In present work, both intra- and inter- molecular aliphatic H-bond interactions stabilize piperidinium based ionic liquids (ILs: MPDNP, PPDNP, BPDNP and HPDNP) and play crucial role on physical properties of these ILs. Further, the significance of multiple intermolecular aliphatic H-bonding interactions in the formation of molecular clusters, ion-pair, dimeric ion-pairs, and also corrugated sheet array of ILs has been investigated here. UV–vis study of these ILs has also been performed to understand the electronic properties of these ILs in solution. The DSC, TGA, SCXRD, vibrational spectroscopic techniques have been employed to understand the effect of intra and intermolecular aliphatic hydrogen bonding interaction on physical property and molecular cluster formation of ILs in their ambient phases. The DSC and TGA studies demonstrate that the intermolecular interaction between cation and anion remains nearly unvaried on increasing of alkyl chain length but the physical properties of ILs changes. SCXRD and vibrational spectroscopic techniques describe the presence of aliphatic H-bonding interaction between ion pairs, dimeric ion-pairs and corrugated sheet having contacts in the range 2.46–2.63 Å. NBO analysis is performed to calculate the second order stabilization energy for better understanding of the intramolecular interactions at a molecular level. The second order stabilization energy for the transfer lone pair charge of oxygen to antibonding orbital of CH is measured in the range of 3.46–3.73 Kcal/mol for ILs. Topological and ab initio molecular dynamics (AIMD) simulations studies are performed to get closer insight of underlying interactions and the stability of ILs. AIMD study depicts that the total energy of IL attains a maximum of −1045.84 a.u. close to 100 fs, whereas relatively low energy is measured between 250 and 350 fs.
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•Solvent specific ground state and excited state aggregates of BISCH molecule in solution.•The effect of solvent on aggregation process is explained on the basis of solute–solute ...interaction.•The effect of molecular geometry depending upon interaction sites of BISCH with solvent is discussed.•AIM, ELF, LOL, ALIE, MESP and NCI show the contribution of hydrogen bonding interaction for their stability.•AIMD demonstrates nature and properties of non-covalent interactions for stabilizing the nano-aggregated system.
Herein, we have demonstrated the solvent specific ground state and excited state aggregates of the molecule ((1E,2E)-1,2-bis((E)-3-phenylallylidene)hydrazine: BISCH) in solution. The nature of aggregation at ground state and excited state is different in H2O solvent. The rate of aggregation in water is calculated from steady state absorption and fluorescence spectroscopy respectively. Excited state fluorescence behaviour contributed from aggregates and non-aggregates species have been identified by time resolved fluorescence spectroscopy in H2O. Aggregation is highly sensitive towards solvent polarity and nature of solvent. The effect of solvent on aggregation process has been discussed and explained on the basis of relative change of hydrophobic and hydrophilic interaction of solute-solvents in solution. Further, J-type aggregation of BISCH is also observed in H2O. Further, using 1st order aggregation kinetic model for ground and excited state,) aggregation rate constant has been calculated and found to 8.0x10-4s−1 ((kagg@312 nm) and 1.2x10-4s−1 (kagg@413 nm) respectively. Effect on molecular geometry depending upon Interaction sites of BISCH and solvent molecule is also discussed with the results from DFT calculation. NBO, NCI, DOS, MESP along with various topological analysis are performed for BISCH in water. For BISCH…water molecular system, NBO interaction is observed due to delocalization of lone pair of O35 and N36 to antibonding of H37-O38 and H40-O41, respectively. ELF, LOL, AIM and ALIE calculation are employed to locate the site and magnitude of hydrogen bonding interactions. The AIMD study for BISCH in water shows minimum of the total energy between 125 and 175 fs and 225–275 fs. N…H-O hydrogen bonding interactions such as N36-H40 and N35-H37 varies from 1.8 to 2.6 Å during the molecular dynamics simulation.
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•Sective photo dissociative CC bond of highly photoactive bis-2-benzylidenemalononitrile (BBM) is observed under UV irradiation.•The CC bond is more polarizable, highly active and ...susceptible for photodissociation.•Product A (2-(4-formylbenzylidene)malononitrile), formed by the selective CC bond photodissociation and has been isolated.•The pseudo 1st order kinetics and dipolar mechanism.
Photophysical study of highly photoactive bis-2-benzylidenemalononitrile (BBM) has been investigated in solution using UV–vis, fluorescence and NMR spectroscopic techniques. The seletive photodissociation can be attributed to the presence of highly polarized CC bond, attached to dicyno groups (CN). Nevertheless, the observed photodissociation of BBM is highly solvent specific and temperature sensitive. The product A (2-(4-formylbenzylidene)malononitrile), formed by the selective photodissociation of BBM under UV irradiation has been isolated and identified by NMR studies. The photodissociation followed the pseudo 1st order kinetics with a rate constant (k) 10−3-10-4.s-1. Moreover the mechanistic study of selective photodissociation of bis-2-benzylidenemalononitrile (BBM) has been investigated and found to follow the dipolar mechanism path during photochemical reaction.
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•Hy34DC as a photoacid and intramolecular charge transfer (ICT) probe for proton transfer process from solute to solvent at the ground and excited state.•Microsolvation and ...intermolecular H-bonding interactions play a significant role in enhancing the proton transfer process.•Solvent-dependent enhancement of proton transfer process is observed comparing the relative intensity of ICT band from UV–Vis results at ground state.•Both Protonated and deprotonated forms of Hy34DC are co-existed both at ground and excited state depending upon the nature and polarity of solvents.
The present work recognises 2-(3,4-Dihydroxybenzylidene)malononitrile (Hy34DC) as a photoacid and intramolecular charge transfer (ICT) probe for proton transfer process from solute to solvent at the ground and excited state. Microsolvation and intermolecular H-bonding interactions play a significant role in enhancing the proton transfer process. Solvent-dependent enhancement of proton transfer process is observed comparing the relative intensity of ICT band from UV–Vis results at ground state. Solvent-specific dual fluorescence properties of Hy34DC are also detected in solution. Polar protic solvents boost the proton transfer process from solute to solvent via intermolecular H-bonding interaction. DFT calculations are also performed to investigate the solvent-dependent solute–solvent interactions.
Two new di-cationic imidazolium based ionic liquids (ILs) containing chloride, (bisImCl), or hexafluorophosphate anions (bisImPF6) have been synthesized and characterized by FT-Raman and 1H- and 13C ...NMR spectroscopies. The p-xylyl group acts a spacer between two imidazolium rings in the cation. The influence of the anions on thermal properties of the compounds has been investigated. Both bisImCl and bisImPF6 have shown good thermal stability up to at least 280 °C. Intermolecular and cation-anion interactions have been investigated by NMR spectroscopy. B3LYP/6-311++G∗∗ calculations have optimized the structure of bisIm cation with both anions. Both Cl are found to be in a monodentate coordination, while in bisImPF6 only one PF6 group presents monodentate coordination. AIM calculations at the same level of theory have evidenced a higher number of interactions in bisImPF6, as compared to bisImCl. A complete assignment of the vibrational frequencies for the cation, bisImCl and bisImPF6 are here reported together with a set of harmonic scaled force constants calculated for the cation and bisImCl. Further, polarizability (α) and the static first hyperpolarizabilities (β) of these ILs are calculated by different DFT functionals in order to understand nonlinear optical (NLO) properties. It is observed an inverse correlation between the predicted β value and the HOMO-LUMO energy difference (Δε) from two state models. The high gap value observed for bisImPF6 justifies its low reactivity, as supported by the high number of interactions predicted for this ionic liquid.
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•Two di-cationic ionic liquid (bisImCl) and (bisImPF6) were synthesized.•DFT calculations suggest monodentate coordinations of both Cl in bisImCl.•FT-Raman and NMR Spectroscopy of bisImCl and bisImPF6 are recorded and analyzed.•Complete assignments for cation and bisImCl and bisImPF6 have been reported.•bisImCl and bisImPF6 have shown good thermal stability.
In present work, we have been investigated the thermochromism, keto-enol tautomerization, J-type aggregation and aggregation induced enhanced fluorescence (AIEF) in a single schiff base molecule ...(HNBzP) along with excited state intramolecular proton transfer (ESIPT) process. It is observed that keto-enol tautomerization plays an important role on thermochromism, J-type aggregation and aggregation induced enhanced fluorescence (AIEF) process in solution. From UV–Vis and fluorescence studies, J-type aggregation is observed and shows the aggregation induce enhanced fluorescence (AIEF) behaviour in solusion. The excited state intramolecular proton transfer (ESIPT) process is investigated in different solvents. Optimized geometry and electronic properties are calculated by DFT method for better understanding at molecular level.
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•J-type aggregation and thermochromism•Aggregation induced enhanced fluorescence (AIEF) in solution•Role of keto-enol tautomerization on J-type aggregation
•Concentration dependent aggregation behavior of Salen-type Schiff base (BIHyDE).•Influence of dipolar state and intermolecular interaction.•Strong aggregation observed ground and excited state in ...solution.•UU-Vis, Fluorescence (Steady state and Time resolved) support the strong aggregation.
Aggregation behavior of push-pull salen-type schiff base (BIHyDE) in different solvents at ground and excited state, has been investigated. At ground state, lower energy absorption band is suppressed during concentration dependent UV-Vis study in CHCl3 solution. The broadening of lower energy emission band is observed during concentration dependent fluorescent study in CHCl3 solution. Interestingly, fluorescence life time of BIHyDE in solution is also altered during concentration dependent fluorescence study in CHCl3 solvent. Similar aggregation is also observed at ground and excited state in ACN solvent. Dipolar state and intermolecular dipolar interaction of BIHyDE molecule highly influence towards strong aggregation process and orientation of molecule in solution. Ground state and excited state optical properties are highly influenced by concentration of push-pull salen-type schiff base (BIHyDE) in different solvents.
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•Photodissociation kinetics of BBM is investigated in different micelle concentration.•Micelle concentration plays significant role on photodissociation kinetics.•In micelle, ...hydrophobic region plays important role on enhancing rate of photodissociation.•In hydrophobic environment (Specially CMC condition), rate of photodissociation is higher compared to polar solvents.
In present work, photodissociation kinetics of selective CC bond in BBM is investigated in different micelles concentration. In polar solvents, rate of photodissociation (k) is relatively lower compared to H2O solvent under similar condition. The rate of photodissociation (k) is enhanced with increase of aqueous CTAB concentration and found to be highly sensitive to aqueous CTAB concentration. It is clear that micelle concentration and hydrophobic region plays significant role on enhancing rate of photodissociation. Crucial role of hydrophobic region in micelle has been discussed and confirmed by experimental results.
Three quinazoline based small molecules showed global upregulation of miRNA expression with a selective enrichment of tumor suppressor miRNAs. The target genes of the upregulated miRNAs were ...predicted to be enriched for apoptotic pathways. Apoptotic induction following treatment with quinazoline compounds was confirmed by in cellulo studies. Thus, these small molecules having the core structural moiety (2,4-diphenyl-quinazoline) can be used as scaffolds to design activators of miRNA expression paving the way for novel anti-cancer drugs.