Experimental and molecular modelling demonstration of effective DNA and protein binding as well as anticancer potential of two mononuclear Cu(II) and Co(II) complexes with isothiocyanate and azide as anionic residues.

In the present study, one mononuclear Cu(II) [CuL(SCN)] (1) and one mononuclear Co(II) [CoLN3] (2) complexes, with a Schiff base ligand (HL) formed by condensation of 2-picolylamine and salicylaldehyde, have been successfully developed and structurally characterized. The square planer geometry of both complexes is fulfilled by the coordination of one deprotonated ligand and one ancillary ligand SCN-(1) or N3-(2) to the metal centre. Binding affinities of both complexes with deoxyribonucleic acid (DNA) and human serum albumin (HSA) are investigated using several biophysical and spectroscopic techniques. High values of the macromolecule-complex binding constants and other results confirm the effectiveness of both complexes towards binding with DNA and HSA. The determined values of the thermodynamic parameters support spontaneous interactions of both complexes with HSA, while fluorescence displacement and DNA melting studies establish groove-binding interactions with DNA for both complexes 1 and 2. The molecular modelling study validates the experimental findings. Both complexes are subjected to an MTT test establishing the anticancer property of complex 1 with lower risk to normal cells, confirmed by the IC50 values of the complex for HeLa cancer cells and HEK normal cells. Finally, a nuclear staining analysis reveals that the complexes have caused apoptotic cell death.

Effect of ionic strength on aggregation of nile red and coumarin 30 in aqueous medium: primary kinetic salt effect or salting-out effect?

The effect of ionic strength on the aggregation of planar dyes like nile red (NR) and coumarin-30 (C30) in aqueous medium has been explored. The dyes are known to undergo dimerization, resulting in fading of their respective colors in the visible range. The present study demonstrates that the fading process is accelerated appreciably upon increasing ionic strength of the solution through addition of soluble salts. Experiments consist of variation of cations (Na+, Mg2+ and Al3+) with different valencies in a series of salts keeping the anion same and a similar set with a variation of anions (NO3-, SO42- and PO43-), keeping the cation same. The question of involvement of 'primary kinetic salt effect' or 'salting-out effect' for accelerating the aggregation process has also been resolved. Using Na+, K+ and NH4+ ions with the same counterpart NO3-, our experimental results do not show any differential effect, in terms of making the aggregation process faster, and hence rule out any effect of Hofmeister series on the self-aggregation process. The detailed study explicitly establishes that it is the 'primary kinetic salt effect' and not the 'salting-out effect' that is involved in the present case.

Exploration of Self-Aggregation of Coumarin 7 and Coumarin 30 in Water: Role of ß-Cyclodextrin as a Modulator.

Steady-state and time-resolved spectroscopic studies demonstrate that two members of the coumarin class of dyes, coumarin 7 (C7) and coumarin 30 (C30), undergo self-aggregation in water. The development of hypsochromically shifted new absorption bands in addition to the existing monomer bands with an increase in concentration of the dyes in an aqueous medium suggests that the aggregates are of H-type. An absorption-based kinetic study reveals that the rate of aggregation of C30 is an order of magnitude faster than that of C7. Second-order rate kinetics, as obtained from the half-life (t1/2) data, implies that the aggregates are dimeric in nature. Observations of isosbestic points in area-normalized absorption spectra (ANAS) and isoemissive points in area-normalized fluorescence excitation spectra (ANFES) and time-resolved area-normalized emission spectra (TRANES) establish that ground-state monomer ⇌ dimer equilibria for both of the systems are preserved in the photoexcited state. The present study further establishes that ß-cyclodextrin is the most efficient of the three common cyclodextrins in shifting the equilibria toward the monomer by encapsulating the monomers within its cavity, making ß-CD a convenient modulator to control the self-aggregation process. Dynamic light scattering (DLS), quantum chemical calculations, and molecular docking studies provide further support to our propositions.

Hydroxyl Group-Directed Solvation of Excited-State Intramolecular Proton Transfer Probes in Water: A Demonstration from the Fluorescence Anisotropy of Hydroxyflavones.

Formation of a probe-solvent network resulting in unusually high fluorescence anisotropy (FA) of an excited-state intramolecular proton transfer (ESIPT) probe, 3-hydroxyflavone (3HF), in water prompted us to explore the solvation patterns on its 7-hydroxy (7HF) and 6-hydroxy (6HF) positional analogues. In the present study, it was observed that 7HF exhibits a lower FA than 3HF does in water, implying that the volume of the 7HF-water cluster is less than that of the 3HF-water cluster. Experimental and computational results led us to propose that 7HF forms its water cluster at the molecular periphery in contrast to the projected-out structure in case of the 3HF-water cluster. Density functional theory (DFT)-based quantum chemical calculations provide an approach for the differential solvation patterns of 3HF and 7HF. 6HF, a non-ESIPT probe, exhibits very low FA in water compared with both 3HF and 7HF. This study demonstrates that proper positioning of the hydroxyl group and its participation in the extended π-conjugation within the molecule dictate the formation of the solvated cluster endorsing directed solvation.

Switching from endogenous to exogenous delivery of a model drug to DNA through micellar engineering.

A potential strategy has been demonstrated, for the first time, for switching the mode of delivery of drugs or small molecular systems from endogenous to exogenous, simply by engineering the chain length of micellar carriers. Ethidium bromide (EB) is exploited as the model drug which has been successfully delivered to natural DNA through endogenous and exogenous modes by tuning the chain length of anionic sodium n-alkyl sulfate micelles. ß-cyclodextrin (ß-CD) is exploited as an extrinsic stimulant for the exogenous delivery of EB to DNA. Multi-spectroscopic techniques involving absorption, emission, fluorescence anisotropy, fluorescence decay analysis, circular dichroism, DNA helix melting etc. have established tuning of the delivery mode between endogenous and exogenous. Differential binding affinity of the model drug with different micelles of varying chain length relative to that with DNA is capitalized to make the switching feasible. Although endogenous mode avoids external stimulant and associated problems, a regulation of the stimulant concentration makes the other mode controllable and quantitative. With appropriate choice of carrier micelle and modulation of this developed strategy can radically change the therapeutic research enabling one to take a control over the drug delivery mode to exploit the advantage of one or the other selectively, whenever required.

Origin of Unusually High Fluorescence Anisotropy of 3-Hydroxyflavone in Water: Formation of Probe-Solvent Cage-like Cluster.

Based on the unusually high fluorescence anisotropy (FA) of 3-hydroxyflavone (3HF) in water medium in contrast to the very low FA of its methoxy counterpart (3MF), our proposition invoked formation of an intermolecular hydrogen-bonded cage-like probe-solvent cluster of 3HF in water. In the present work, ab-initio DFT-based quantum chemical calculations have been exploited to provide a foundation for our interpretation. Ground-state optimization of 3HF with varying numbers of water molecules leads to the formation of a cage-like or loop-like probe-water cluster. Our calculations reveal that the structures with four to five water molecules are stabilized to the maximum extent. Classical molecular dynamics simulations reveal that the rotational dynamics of 3HF is much slower in water compared to that in alkane medium, which also goes in favor of the probe-solvent cluster formation in water medium. Apart from the theoretical studies, an indirect experimental approach has been adopted to substantiate formation of the probe-water cluster. The atypical observation of reduced FA of 3HF entrapped in micelles relative to that of the fluorophore in water implies disruption of the probe-water cluster with the addition of micelles, corroborating our original proposition of formation of an intermolecularly hydrogen-bonded 3HF-water cluster.

Aggregation of Nile Red in Water: Prevention through Encapsulation in ß-Cyclodextrin.

The present work, based on various spectroscopic investigations, vividly demonstrates the self-association of Nile red (NR) in aqueous medium. The rapid decrease in the absorbance as well as emission of NR in water bears the signature of the aggregation process. Appearance of a new blue-shifted absorption band in addition to the original one and a drastic decrease in the emission intensity imply that the aggregation is of H-type. Poor solubility of NR in water, hydrophobic interaction, and the planar structure of the dye are ascribed to favor the formation of the aggregate in the aqueous medium. Absorption-based kinetic studies reveal the aggregation process to be second order, thereby establishing the aggregate to be a dimer. Similar kinetic profiles of the absorbance of NR in the presence and absence of light confirm that the aggregation process is not photoassisted. The presence of an isosbestic point in the absorbance spectra and an isoemissive point in the time-resolved area normalized emission spectra bears the evidence of equilibrium between the dimeric and the monomeric species of NR in the ground state as well as in the photoexcited state. Encapsulation of the monomer of NR within the hydrophobic cavity of ß-cyclodextrin is demonstrated to prevent the aggregation process.

Managing efficacy and toxicity of drugs: Targeted delivery and excretion.

Medicine is a natural companion of mankind in the present era for mere survival from the deadly diseases in ever-increasing polluted environments. Hence, in recent years, major focus of pharmaceutical, medicinal and biophysical research has been navigated in exploring and developing new and simple avenues to enhance the efficacy of the administered drugs on one hand and to get rid of, or at least reduce, the toxic side effects of the excess drugs accumulated in human body on the other. A potential approach to amplify the efficacy of the administered drug is to develop proficient targeted drug delivery systems (DDSs). This review provides an essence of some newly developed simple but prospective strategies on enhancing the efficacy of drugs/bioactive molecules exploiting various drug delivery systems like micelles, cyclodextrins, liposomes etc. to serve the purpose of targeted delivery towards DNA, by endogenous and/or exogenous means. Improved bio-availability and solubilization of ionic drugs within the less polar target regions from the bulk aqueous phase has also been achieved through the introduction of some physiologically permissible salts. In the other context, in vitro and in vivo studies demonstrate a simple technique for easy removal of the excess adsorbed drug molecules from the cell membranes/lipid bilayers by exploiting health-amiable supramolecular assemblies. In this review, we summarize the recent experimental findings, mostly from our lab, encompassing the development of simple biocompatible methods to enhance the benevolent role of drugs through their safe, effective and convenient administration. It also presents easy and effective means to remove the excess adsorbed drugs from human body to diminish their malign effects. These prospective approaches of drug delivery and excretion of drug molecules have promising roles to play from both physicochemical and pharmaceutical perspectives, ensuring enhanced bioavailability of drugs as well as disposing of drug-induced adverse side effects.

Unraveling the binding interaction of a bioactive pyrazole-based probe with serum proteins: Relative concentration dependent 1:1 and 2:1 probe-protein stoichiometries.

Molecular interactions and binding of probes/drugs with biomacromolecular systems are of fundamental importance in understanding the mechanism of action and hence designing of proactive drugs. In the present study, binding interactions of a biologically potent fluorophore, (E)-1,5-diphenyl-3-styryl-4,5-dihydro-1H-pyrazole (DSDP) with two serum transport proteins, human serum albumin and bovine serum albumin, have been investigated exploiting multi-spectroscopic techniques. The spectrophotometric and fluorometric studies together with fluorescence quenching, fluorescence anisotropy, urea induced denaturation studies and fluorescence lifetime measurements reveal strong binding of DSDP with both the plasma proteins. Going beyond the vast literature data mostly providing 1:1 probe-protein complexation, the present investigation portrays 2:1 probe-protein complex formation at higher relative probe concentration. A newer approach has been developed to have an estimate of the binding constants varying the concentration of the protein, instead of the usual practice of varying the probe. The binding constants for the 2:1 DSDP-protein complexes are determined to be 1.37 × 1010 M-2 and 1.47 × 1010 M-2 for HSA and BSA respectively, while those for the 1:1 complexation process come out to be 1.85 × 105 M-1 and 1.73 × 105 M-1 for DSDP-HSA and DSDP-BSA systems respectively. Thermodynamic analysis at different temperatures implies that the forces primarily involved in the binding process are hydrogen bonding and hydrophobic interactions. Competitive replacement studies with known site markers and molecular docking simulations direct to the possible locations and binding energies of DSDP with the two serum proteins, corroborating well with the experimental results.

Photophysics of Anthril in Fluids and Glassy Matrixes.

Photophysics of 9,9'-anthril have been investigated at room temperature and cryogen phase (77 K) exploiting steady state and time-resolved emission techniques together with quantum chemical calculations. Absorption spectra, emission spectra, and emission lifetimes of anthril have been recorded and analyzed in polar ethanol and nonpolar methylcyclohexane media. Both room temperature and cryogenic experiments reveal a single emission band upon excitation at the nπ* absorption band whereas on exciting the system at the ππ* band, dual emission bands have been observed. Characterization of these two fluorescence bands to be originating from near-trans and relaxed skew conformers have been made by monitoring their differential effect on varying the polarity of solvents. Similarly, two phosphorescence bands have been assigned to trans and cis geometries by looking at the change in the emission spectra in the two rigid matrixes of different polarity. Observation of a single isoemissive point in the time-resolved area normalized emission spectroscopy (TRANES) for both fluorescence and phosphorescence emissions unambiguously validates the coexistence of the two conformers in the excited singlet and triplet states, respectively. Qualitative quantum chemical calculations indicate that the S1 and T1 states are responsible for the dual fluorescence and phosphorescence bands. Effortless transitions from the higher excited singlet states (S3 or S2) to the lowest energy excited singlet (S1) state because of their energy proximity discard any possibility of S2 emission, consistent with two other 1,2-dicarbonyl compounds like α-furil and 2,2'-pyridil, while going in contrast to the observation of S2 emissions from benzil and α-naphthil. On the basis of the vivid photophysical studies on five probes in fluid media and 77 K glassy matrixes, we conclude that exhibition of the S2 emission for aromatic 1,2-dicarbonyl compounds is truly system dependent and not a general phenomenon for all the molecular systems in the series.

Supramolecular Aggregates of Tetraphenylethene-Cored AIEgen toward Mechanoluminescent and Electroluminescent Devices.

Luminescent materials possessing both the mechanoluminescence (MCL) and electroluminescence (EL) properties are the quest for sensing and optoelectronic applications. We report on the synthesis of a new tailor-made luminogen, 1,2-bis(4-(1-([1,1'-biphenyl]-4-yl)-2,2-diphenylvinyl)phenyl)-1,2-diphenylethene (TPE 5), using Suzuki coupling reaction with high yield. An aggregation-induced emission (AIE) active complex TPE 5 forms supramolecular spherical aggregates at the air-water interface of a Langmuir trough. As a consequence, a large enhancement of luminescence is obtained from the mono- and multilayer Langmuir-Blodgett films of TPE 5 owing to the AIE effect. The luminogen TPE 5 exhibits a reversible MCL response, displaying photoluminescence switching due to change in the crystalline states under external stimuli. The unique feature of luminescence enhancement upon aggregate formation is utilized for the fabrication of light-emitting diodes with low threshold voltage using supramolecular aggregates as the active layer. This work demonstrates an efficient strategy for obtaining controlled supramolecular aggregates of AIEgen with a potential in the dual applications of MCL and EL.

Photophysics of a coumarin based Schiff base in solvents of varying polarities.

The present work reports detailed photophysics of a coumarin based Schiff base, namely, (E)-7-(((8-hydroxyquinolin-2-yl)methylene)amino)-4-methyl-2H-chromen-2-one (HMC) in different solvents of varying polarity exploiting steady state absorption, fluorescence and time resolved fluorescence spectroscopy. The dominant photophysical features of HMC are discussed in terms of emission from an intramolecular charge transfer (ICT) excited state. Molecular orbital (MO) diagrams as obtained from DFT based computational analysis confirms the occurrence of charge transfer from 8'-hydroxy quinoline moiety of the molecule to the coumarin part. The notable difference in the photophysical response of HMC from its analogous coumarin (C480) lies in a lower magnitude of fluorescence quantum yield of the former, particularly in the solvents of low polarity, which is rationalized by considering the higher rate of non-radiative decay of HMC in apolar solvents. Phosphorescence emission as well as phosphorescence lifetime of HMC has also been reported in 77K frozen matrix.

Interaction of a bioactive pyrazole derivative with calf thymus DNA: Deciphering the mode of binding by multi-spectroscopic and molecular docking investigations.

Deoxyribonuclic acid (DNA) is the most relevant intracellular target for a wide variety of anticancer and antibiotic drugs. Elucidating the binding interaction of small bioactive molecules with DNA provides a structural guideline for designing new drugs with improved selectivity and superior clinical efficacy. In the present work interaction of a newly synthesized biologically relevant fluorophore, namely, (E)-1,5-diphenyl-3-styryl-4,5-dihydro-1H-pyrazole (DSDP) with calf thymus DNA (ctDNA) has been investigated vividly through a number of in vitro studies. Noteworthy modifications in the UV-Vis absorption and emission spectra reveal the formation of the probe-ctDNA complex. Several other spectroscopic experiments such as circular dichromism (CD), iodide induced quenching, competitive binding assay with known groove binder probe, 3-hydroxyflavone (3HF), time resolved fluorescence decay measurements, thermometric experiment in connection with the helix melting of ctDNA etc. unequivocally ascertain the groove binding interaction of DSDP with ctDNA. Determination of the thermodynamic parameters through temperature variation study implies the dominant role of hydrophobic interaction in the probe-DNA binding process. Inappreciable change in the CD spectrum of ctDNA with the addition of DSDP suggests that binding of the probe with the DNA does not lead to a significant modification in the DNA conformation. In-silico molecular docking simulation corroborates the experimental findings and depicts that DSDP favorably binds to the minor groove region of the biomacromolecule.

Dehydrogenation induced inhibition of intramolecular charge transfer in substituted pyrazoline analogues.

The detailed photophysics of (E)-1,5-diphenyl-3-styryl-4,5-dihydro-1H-pyrazole (DSDP) and (E)-1,5-diphenyl-3-styryl-1H-pyrazole (DSP) has been investigated and compared to demonstrate the drastic modification of the photophysics upon dehydrogenation of the pyrazoline ring. While DSDP gives dual absorption and dual emission bands corresponding to the locally excited (LE) and the intramolecular charge transfer (ICT) species, DSP yields single absorption and emission bands for the locally excited species only. Comparative steady state and time resolved fluorometric studies reveal that aromatization of the pyrazoline ring inhibits the formation of the ICT species. Quantum chemical calculations corroborate and rationalize the inhibition of the ICT process upon aromatization through depiction of the differential electronic distributions in the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the two fluorophores.

Exploration of photophysics of 2,2'-pyridil at room temperature and 77 K: a combined spectroscopic and quantum chemical approach.

The photophysics of 2,2'-pyridil has been explored thoroughly using steady state and time resolved fluorometric techniques at room temperature (RT) in liquid media as well as in glassy matrices at cryogenic temperature (77 K). Ethanol and methylcyclohexane are exploited for this purpose, as polar and non-polar media respectively. Notwithstanding the observation of multiple emissions from the fluorophore, the experiments unequivocally rule out emission from excited singlet states other than the S1 state, consistent with Kasha's rule. Among 1,2-dicarbonyl molecular systems, this behavior resembles that of α-furil, while it contradicts that of benzil and α-naphthil which exhibit S2 emissions. The dual fluorescence and dual phosphorescence of the fluorophore are ascribed to the emissions originating from the two conformers, namely near-trans and relaxed skew. Coexistence of the two conformers is substantiated by time resolved area normalized emission spectroscopy (TRANES) at both RT and 77 K. The potential energy curves (PECs) simulated from calculations based on density functional theory and its time dependent extension provide adequate support to the experimental observations.

Endogenous Activation-Induced Delivery of a Bioactive Photosensitizer from a Micellar Carrier to Natural DNA.

The photophysics of phenosafranin (PSF), a member of the photosensitizer phenazinium family, has been explored in nonionic Triton X-165 (TX-165) micelle, calf thymus DNA (ctDNA), and a composite environment consisting of both micelle and DNA, using diverse spectroscopic techniques of both steady-state and time-resolved natures, to divulge the binding interactions of the probe with different hosts. The vivid experimental results demonstrate that PSF binds with both micelle and DNA; however, the binding affinity of the probe is much higher toward the DNA. When micelle-carried PSF comes in proximity to ctDNA, PSF gets released from the micellar environment and intercalates with the DNA base pairs. Endogenous activation, in terms of a higher binding affinity of PSF toward ctDNA relative to that toward the micelle, is ascribed to be responsible for this transfer. Thus, this article demonstrates endogenous transfer of a bioactive molecular probe from a micellar nanocarrier to natural DNA. As the carrier micelle (TX-165) does not perturb the structure of the DNA, this work proposes that it can be used promisingly for the purpose of safe delivery of drugs. The study is expected to stimulate the generation of and/or search for advanced micelle-based carrier systems for delivery of bioactive molecular systems to biological targets like DNA.

Relocation of a biological photosensitizer from non-ionic micellar carrier to DNA: A multispectroscopic investigation.

Relocation of a bioactive photosensitizer, namely phenosafranin (PSF), from the phenazinium family, has been demonstrated from non-ionic micellar carrier to the DNA. For the purpose, interaction of micelle-bound PSF with calf thymus DNA (ctDNA) has been investigated vividly exploiting various spectroscopic techniques like absorption, steady state and time resolved emission, fluorescence anisotropy, circular dichroism etc. Experimental outcomes reveal that PSF binds strongly with both the micelle as well as the DNA. In the presence of DNA, however, relocation of the micelle-carried PSF occurs from the micelle to the DNA. Competitive binding of the probe between micelle and the DNA is assigned responsible for this relocation. Circular dichroism spectral measurements reflect that the DNA conformation remains intact in the presence of the micelle advocating that the non-ionic micelles can safely be used for the drug delivery purpose. The work is expected to encourage development of newer carriers for DNA targeted drug delivery.

Photophysics of α-furil at room temperature and 77 K: Spectroscopic and quantum chemical studies.

Steady state and time resolved spectroscopic measurements have been exploited to assign the emissions from different conformations of α-furil (2, 2'-furil) in solution phase at room temperature as well as cryogen (liquid nitrogen, LN2) frozen matrices of ethanol and methylcyclohexane. Room temperature studies reveal a single fluorescence from the trans-planar conformer of the fluorophore or two fluorescence bands coming from the trans-planar and the relaxed skew forms depending on excitation at the nπ(∗) or the ππ(∗) absorption band, respectively. Together with the fluorescence bands, the LN2 studies in both the solvents unambiguously ascertain two phosphorescence emissions with lifetimes 5 ± 0.3 ms (trans-planar triplet) and 81 ± 3 ms (relaxed skew triplet). Quantum chemical calculations have been performed using density functional theory at CAM-B3LYP/6-311++G(∗∗) level to prop up the spectroscopic surveillance. The simulated potential energy curves (PECs) illustrate that α-furil is capable of giving two emissions from each of the S1 and the T1 states-one corresponding to the trans-planar and the other to the relaxed skew conformation. Contrary to the other 1,2-dicarbonyl molecular systems like benzil and α-naphthil, α-furil does not exhibit any fluorescence from its second excited singlet (S2) state. This is ascribed to the proximity of the minimum of the PEC of the S2 state and the hill-top of the PEC of the S1 state.

Fabrication of mixed phase TiO2 heterojunction nanorods and their enhanced photoactivities.

Substantial efforts have been made in recent times in solving the major limiting factors affecting the efficiency of a photocatalyst. The fabrication of efficient junction architectures is one of the viable approaches to resolve this setback. We have developed a facile and systematic approach for the synthesis of anatase TiO2 () nanoparticles and 1-D anatase and rutile TiO2 () heterojunction nanorods to enhance the interfacial contact area by adjusting the titanium(iv) butoxide (TBOT) to titanium chloride (TiCl4) volume ratio. Their narrower band gap, increasing surface area and anatase phase composition engineered by adjusting the relative concentrations of titanium butoxide (TBOT) and titanium chloride (TiCl4) (TBOT/TiCl4, 1 : 0, 1 : 0.25, 1 : 1 and 1 : 4 v/v for , , and respectively) are also addressed. The materials showed impressive photocatalytic activity for H2 evolution from water/methanol and the photodegradation of organic pollutants like rhodamine B (RhB) and methylene blue (MB) dyes. showed superior activity (16.4 mmol g(-1) h(-1)) with an apparent quantum efficiency (AQE) of 7.7% together with its long-term stability. This is attributed to the synergistic effect observed in the mixed phase nanorod heterojunction photocatalyst. Methyl viologen (MV(2+)) has been used as a probe to elucidate the photocatalytic activities and highlight the heterojunction driven separation of photo-excited charge carriers for enhanced hydrogen production.

Impact of Structural Modification on the Photophysical Response of Benzoquinoline Fluorophores.

Structural influence on the photophysical behavior of two pairs of molecular systems from the biologically potent benzoquinoline family, namely, dimethyl-3-(4-chlorophenyl)-3,4-dihydrobenzo[f]-quinoline-1,2-dicarboxylate, dimethyl-3-(2,6-dichlorophenyl)-3,4-dihydrobenzo[f]quinoline-1,2-dicarboxylate and their corresponding dehydrogenated analogues has been investigated exploiting experimental as well as computational techniques. The study unveils that dehydrogenation in the heterocyclic rings of the studied quinoline derivatives modifies their photophysics radically. Experimental observations imply that the photophysical behavior of the dihydro analogues is governed by the intramolecular charge transfer (ICT) process. However, the ICT process is restricted significantly by the dehydrogenation of the heterocyclic rings. Computational exertion leads to the proposition that the change in the electronic distribution in these molecular systems on dehydrogenation is the rationale behind the dramatic modification of their photophysics.