Solvatochromic Shifts Research Articles

Evolution of High-Affinity ssDNA Sequence to Carbon Nanotube

Colloidal ssDNA-wrapped single walled carbon nanotube (ssDNA-SWCNT) has been used as the second near-infrared (NIR-II, 1000 -1700 nm) fluorescent nanoprobes with outstanding biocompatibility, and acts as various optical nano sensors for biological analytes such as a dopamine and serotonin. The stability and affinity of ssDNA on the SWCNT surface significantly depends on the sequence of ssDNA, however the large-scale quantitative analysis between ssDNA sequence library, which has high affinity to the SWCNT surface, was repeatedly selected from a random ssDNA(N30) library (~1018) and the resulting sequence data was analyzed. The binding affinity of ssDNA to SWCNT was quantitatively characterized. To quantitatively analyze the kinetics of the process which occurs solvatochromic shift by sodium cholate, assumed the dynamics follow a first-order kinetic model and fit the experimental data using exponential regression, from which decay time constants were determined. As a result, the highest binding affinity of ssDNA to SWCNT was quantitatively characterized by time constant (1.5 X106 sec) which increased by 100 times compared to the N30 random library. Through analysis of the ssDNA sequences with high affinity for the SWCNT surface, we found that the sequences contain high contents of cytosine and adenine nucleotides and complementary base pairs appeared at distance of 5 to 8 bases. This novel sequence library can be applied for the preparation of the ultra-stable ssDNA-SWCNT dispersion and used for anchoring surface ligands for SWCNT as biosensor. Figure 1

Multiparametric Investigations on Solvation Behaviour and Spectral Shifts of Symmetric Aromatic Diselenides: A case study of Diphenyldiselenide

ABSTRACT Decorating symmetric aromatic diselenide motif such as in diphenyldiselenide (DPDSe) with diverse supra-functionalities provides a plethora of bioactivities for pharmacological applications. Solvent studies of bioactive molecules are vital descriptors for their drug development as these can predict the drug–target interaction. This study aims to evaluate the influence of intermolecular interactional forces on the solvation behaviour and spectral shifts of DPDSe. The solvation behaviour of DPDSe was evaluated primarily via solvent polarity and solvent parameters. The observed solvatochromic shifts were analysed with various solvent study models, of which Kamlet–Taft and Catalan models were found to be most suitable for describing intermolecular interactions of DPDSe. The experimental data suggest an overall red shift with increasing solvent polarity. Moreover, data analysis using solvatochromic models predict negative coefficients for solvent dipolarity (π*) and solvent polarisabilities (SP) and (SdP). The studied dipole moment values indicate the more polar nature of DPDSe in the excited state relative to the ground state, further corroborating the observed bathochromic shift with increasing solvent polarity.

Elucidating the conformational change and electronic absorption spectrum of p-dimethylamino-cinnamaldehyde merocyanine across different solvent polarities.

We present a theoretical study on the structural and electronic properties of the p-dimethylamino-cinnamaldehyde (DMACA) merocyanine molecule in solvents of different polarities by combining the free energy gradient and the average solvent electrostatic configuration methods via an iterative procedure based on the sequential quantum mechanics/molecular mechanics hybrid methodology. Studying such a system in solution is a crucial step for understanding the solvent effects on its properties, which can have implications in fields such as optoelectronics and biophysics. We found that the DMACA molecule presents different geometries in nonpolar and polar solvents, changing from a polyene-like structure with a pyramidal dimethylamino group (in gas phase or nonpolar solvents) to a cyanine-like structure with a planar dimethylamino group in water due to the stabilizing effect of hydrogen bonds between DMACA and water. The molecular absorption spectrum showed a significant change, increasing solvent polarity with a large shift of the lower energy band, while the other two low lying bands did not shift significantly. The study accurately described the solvatochromic shift of the lowest-energy band and analyzed the structure of the excited states in terms of the one-electron transition density matrix, which showed that the dominant excited state (associated with the first lower energy band) is characterized by a local excitation on the benzene ring with charge transfer character to the carbon conjugated segment.

Systematic Photophysical Interaction Studies Between Newly Synthesised Oxazole Derivatives and Silver Nanoparticles: Experimental and DFT Approach.

In this study, the photophysical properties of oxazole derivatives such as 5-(furan-2-yl) -4-tosyloxazole (OX-1) and 5-(2-bromothiazol-4-yl)-4-tosyloxazoles (OX-2) were investigated using theoretical and experimental techniques. The ground and excited state dipole moments were empirically obtained utilising the solvatochromic shift technique and several solvatochromic correlations such as Lippert's, Bakhshiev's, KawskiChamma- Viallet's, and solvent polarity equations. The ground state dipole moments, HOMO-LUMO and molecule electrostatic potential map were also computed using ab initio calculations and evaluated using Gaussian 09 W software. Furthermore, spectroscopic interactions between newly synthesised dyes (OX-1 and OX-2) and freshly synthesised silver nanoparticles (size 40nm) were studied. Increased absorbance and widening of absorption spectra for both dyes in the presence of varied quantities of silver nanoparticles show the potential of dye-nanoparticle interactions. Fluorescence quenching has been detected for both dyes in the presence of colloidal silver nanoparticles, indicating dynamic quenching, and a significant overlap between the absorption and emission spectra of the silver nanoparticle reveals that fluorescence quenching is also due to energy transfer.

Estimation of dipole moments by Solvatochromic shift method, spectroscopic analysis of UV–Visible, HOMO-LUMO, ESP map, Mulliken atomic charges, NBO and NLO properties of benzofuran derivative

Solvatochromic shift method has been used to estimate ground state (μg) and excited state (μe) dipole moments of benzofuran derivative (5NFMOT) at room temperature indifferent solvents. This method involves Lippert, Bakhshiev and Kawski-Chamma-Viallet equations. Reichardt microscopic solvent polarity parameter was used to calculate the change in dipole moment. Effect of solvents on absorption and fluorescence spectra was investigated using Kamlet and Catalan's MLR approach. Computational studies of benzofuran derivative were carried out using Gaussian 16. Geometry optimization was performed using DFT method at 6–311++G (d, p)/B3LYP basis set. UV–Visible spectra have been studied by using TD-DFT method for the same basis set. The μg was obtained from DFT method, whereas μe from TD-DFT method. It has been observed that both from experimentally and theoretically the ground state dipole moment is higher than the excited state dipole moment. HOMO-LUMO surfaces and Mulliken atomic charges have been studied in gas phase and solution. Furthermore, 3D plots of electrostatic potential map are used to identify reactive centers such as electrophilic and nucleophilic sites. NBO analysis is helpful to obtain stability and charge delocalization of the title molecule. Polarizablity, and hyper polarizability values were used to study the NLO properties.

Absorption and fluorescence spectra of new pyrrolo[3,4‐b]quinolizines in condensed phases: A joint experimental and computational study

AbstractNewly synthesized pyrrolo[3,4‐b]quinolizines, blue‐green to orange‐red in fluorescent dye in solutions and yellow to red fluorescent dyes in solid states, were experimentally and computationally investigated for the electronic and fluorescence spectra in solution as well as in solid state. The solvent effects on the absorption and emission spectra were theoretically investigated by the snapshots‐averaged spectra obtained by the first principle molecular dynamics combined with polarizable continuum model (PCM). Alternatively, the solute–solvent interaction effect on the spectra was examined by fragment molecular orbital‐time dependent density functional theory (FMO‐TDDFT) which considered the explicit solute–solvent interactions. The results indicate that the quantitative prediction limitations of PCM and that the solvatochromic shifts in dichloromethane and ethanol were correctly reproduced by FMO‐TDDFT. The luminescence quantum yields of the compounds were analyzed on the excited state potential surface via the S0/S1‐conical intersections.

Constrained Nuclear-Electronic Orbital Density Functional Theory with a Dielectric Continuum Solvent Model.

Solvent effects are crucial for simulating chemical and biological processes in solutions. The continuum solvation model is widely used for incorporating solvent effects with different levels of theoretical descriptions of solutes. For solutes and solutions containing hydrogen atoms, nuclear quantum effects can also be nonnegligible for reliable simulations. In this work, we couple our recently developed constrained nuclear-electronic orbital density functional theory with a dielectric continuum solvation model to cover nuclear quantum effects and solvent effects simultaneously. This approach is applied to the formate ion, where an anomalous solvatochromic shift in C-H stretch frequency was reported in experiments. By using this new approach to account for nuclear quantum effects and solvent effects, we show that the vibrational frequency of the C-H stretch and the solvatochromic shift are accurately described.

Intramolecular charge transfer in bulky “diazabutadiene-M(II)-catecholate” chromophores (M = Ni, Co): A role of a molecular geometry

Two monomeric heteroleptic charge transfer (CT) complexes NiII(3,6-Cat)(DADdipp) (1) and CoII(3,6-Cat)(DADdipp) (2) of “α-diimine-MII-catecholate” general type were prepared in the course of two-step synthetic procedures, based on 3,6-di-tert-butyl-o-benzoquinone (3,6-DTBQ) and 1,4-bis(2,6-di-isopropylphenyl)-1,4-diaza-1,3-butadiene (DADdipp). Square-planar coordination environment in complex 1 enables an implementation of a low energy ligand-to-ligand charge transfer (LL’CT), thus making NIR NiII chromophore (λmax = 1107 nm, in toluene) with high absorptivity of light and a fine sensitivity of CT energy towards solvent polarity (red solvatochromic shift from CH3CN to toluene at 192 nm). Energy of frontiers orbitals and HOMO-LUMO gap of 1 is evaluated in synergy of UV-vis-NIR spectroscopy, cyclic voltammetry, and DFT calculations, with a good accordance of data sets. A significant ligands’ bulkiness provided a tetrahedral distortion of square-planar N2O2 polyhedron of 2 in solutions (CH3CN, CH2Cl2, THF, toluene), that changed CT nature drastically with a concomitant decrease of absorptivity and an elimination of solvatochromism. Electrochemical behavior of studied complexes is defined by the differences in geometry of a coordination environment and corresponding mutual arrangement of metal and ligand orbitals (in solution): one-electron redox processes of square-planar NiII derivative 1 are predominantly ligand-centered, while redox transitions in tetrahedral CoII complex 2 proceed with the substantial participation of cobalt center.

Carbon dots/silicone rubber composites for fluorescence detection of biodiesel in fuel blends

Carbon-based nanoparticles, specifically carbon quantum dots (CQDs), have received growing interest significantly owing to their optical characteristics and production simplicity. Their diverse surface functionality and media solubility have been used to demonstrate their electronic, biological, and chemical applications. CQDs polymer composites have been widely exhibited in the case of functional applications in related areas by using CQDs’ unique properties. On the detection applications of biofuels, numerous spectroscopic and instrumental approaches have been developed in the literature. Here, organic soluble r-CQDs (QY: 72%) have been synthesized to fabricate fluorescent cross-linked silicone composites that are capable of sensing the biodiesel amount in fuel mixtures by solvatochromic shifts. The fluorescent rubber composites were tested with various degrees of biodiesel blends in 24 h for maximal swelling, and approximately 70% absorption was achieved. The capacity to distinguish biodiesel levels has been effectively revealed with an error level of 2.9 nm at the photoluminescence spectral peak, whereas biodiesel levels were as low as 10%. The colorimetric shift of the swollen composites were also sufficient to identify the biodiesel content visually under UV lights.

Analytic geometric gradients for the polarizable density embedding model

AbstractThe polarizable density embedding (PDE) model is an advanced fragment‐based QM/QM embedding model closely related to the earlier polarizable embedding (PE) model. PDE features an improved description of permanent electrostatics and further includes non‐electrostatic repulsion. We present an implementation of analytic geometric gradients for the PDE model, which allows for partial geometry optimizations of QM regions embedded in large molecular environments. We benchmark the quality of structures from PE‐QM and PDE‐QM geometry optimizations on a diverse set of small organic molecules embedded in four solvents. The PDE model performs well when targeting Hartree–Fock calculations, but density functional theory (DFT) calculations prove more challenging. We suggest a hybrid PDE‐LJ model which produces solute–solvent structures of good quality for DFT. Finally, we apply the developed model to a theoretical estimation of the solvatochromic shift on the fluorescence emission energy of the environment‐sensitive 4‐aminophthalimide probe based on state‐specific multiconfigurational PDE‐QM calculations.

Synthesis and spectral investigation of novel 4-aryl-5-(aryldiazenyl)thiazole dyes festooned with fluorene moiety: Experimental and theoretical insight

A series of novel 4-aryl-5-(aryldiazenyl)thiazole dyes 7a-h pendant to fluorene group were synthesized form easily accessible starting materials. The absorption spectra of the synthesized azodyes were recorded in different solvents with variable chemical and physical properties. Structural Elucidation of the synthesized azodyes were carried out by UV–vis, IR and NMR spectroscopies as well as elemental analyses. Different solvent parameters, such as microscopic solvent polarity, Kamlet-Taft and Catalan parameters were employed in order to assess the solute–solvent interactions and the solvatochromic shifts of the absorption maximum of the 4-aryl-5-(aryldiazenyl)thiazole dyes under investigation. The solvent scales constitute the most appropriate method for interpreting the solvatochromic behavior of the synthesized azodyes. Furthermore, the dyes' absorption ability revealed that the substituent effect on UV–vis absorption spectra is strongly influenced by the electronic nature of the substituent on the 1-phenyl ring. It was also observed that the absorption spectra were sensitive to acidic and basic media. The synthesized azo compounds showed spectral changes that revealed that azo tautomers formed at acidic pH while hydrazo tautomers at alkaline pH. To gain a thorough understanding of the stability and geometrical characteristics of the azo-hydrazo tautomers, DFT calculations were also performed on the synthetic dyes.

Solvent Effect on the Photophysical Properties of Terpyridine Incorporating Pyrene Moiety: Estimation of Dipole Moments by Solvatochromic Shift Methods.

The absorption and fluorescence emission spectra of terpyridine incorporating pyrene moiety (Tpy-pyr) have been recorded in extensive variety of solvents having different polarities. The effect of the solvent on the spectral characteristics are examined. It is shown that Tpy-pyr exhibit positive solvatochromism, large Stokes shift values in polar solvents, and fluorescence in the long wavelength region of the visible range. A linear increasing trend with Stokes shift indicates the presence of Tpy-pyr - solvent interaction. The acquired results could be attributed to the formation of excited states with intramolecular charge transfer. The fluorescence quantum yield was drastically reduced in polar protic solvents and the formation of the twisted states with charge transfer was proposed. Both ground and excited state dipole moments (µg and µe) were determined experimentally by Lippert-Mataga, Reichardt, Bilot-Kawski, Bakhshiev and Kawski-Chamma-Viallet solvatochromic methods analyzed on the base of the microscopic solvent polarity functions. The µg and µe dipole moment of Tpy-pyr estimated from density functional theory (DFT) and those determined experimentally from solvatochromic methods are compared and the results are discussed.

Naphthalene and its Derivatives: Efficient Fluorescence Probes for Detecting and Imaging Purposes.

Naphthalene, white crystalline solid having polycyclic aromatic hydrocarbon with characteristic mothball order is naturally present in crucial oils of various plants. Naphthalene derivatives are extensive drug resources and are use as wetting agents, surfactants and as insecticides. These derivatives exhibit unique photo physical and chemical properties. These characteristics make them the most studied group of organic compounds. Naphthalene dyes have rigid plane and large π-electron conjugation. Therefor they have high quantum yield and excellent photostability. Naphthalene based fluorescence probes due to hydrophobic nature exhibit excellent sensing and selectivity properties towards anions and cations and also used as a part of target biomolecules. In conjugated probe system, introducing naphthalene moiety caused improvement in photo-stability. Therefore among various conjugated framework, naphthalene derivatives are considered excellent candidate for the construction of organic electronic appliances. These derivatives are useful for a variety of applications owing to their strong fluorescence, electroactivity and photostability. This article is based upon investigation of photophysical properties of naphthalene derivatives and fluorescence detecting probe of naphthalene. For photophysical properties the techniques under investigation are UV visible spectroscopy and fluorescence spectroscopy. Concentration dependent spectra and solvatochromic shifts on UV visible spectra are also part of discussion.

Carbon-deuterium bonds as reporters of electric fields in solvent and protein environments.

Use of vibrational probes to measure electric fields inside proteins has illuminated the role of electrostatics in biological applications ranging from binding interactions to enzyme catalysis. While prior work focused on strongly absorbing carbonyl and nitrile probes, more recent work has begun exploring weakly absorbing carbon-hydrogen bonds, beginning with measurements of electric fields inside oxidoreductases using the vibrational Stark effect (VSE). Originally, an alcohol dehydrogenase inhibitor containing a deuterated aldehyde was used to measure the field in two directions—on carbonyl and carbon-deuterium (C-D) bonds—in the enzyme active site. Now, several more distinct cases demonstrate how C-D probes map electric fields to vibrational frequency shifts, with new implications for our understanding of the VSE. To probe the field along a different dimension in oxidoreductases, we consider singly deuterated NAD(P)H which reports fields along the hydride transfer axis and whose frequency detection is facilitated by advancements in quantum cascade laser (QCL) technology for infrared spectroscopy. Unusually, the solvatochromic shift for this C-D probe appears opposite to that observed for carbonyls and nitriles; that is, the probe blueshifts in more polar solvents. In another example, the chromophore of green fluorescent protein (GFP) with a deuterated bridge carbon demonstrates similarly unusual frequency shifts in solvent and protein environments, with stronger fields parallel to the C-D dipole causing blueshifts. Observed Stark tuning rates for these molecules are recapitulated by in silico Stark calculations at the B3LYP or ωB97X-D/6-31+G(d) level. Stark tuning rate comparison with other C-D containing molecules including deuterated aldehydes and chloroform-d indicates a large sensitivity of the Stark tuning rate to molecular structure. We demonstrate how properly calibrated C-D probes can be effective reporters of electric fields in applications such as enzyme-catalyzed hydride transfer, biological photophysics and beyond.

SOLVATOCROMISMO E AS ESCALAS EMPÍRICAS DE POLARIDADE DO SOLVENTE: UMA REVISÃO

SOLVATOCHROMISM AND THE EMPIRICAL SCALES OF SOLVENT POLARITY: A REVIEW. The term solvatochromism is used to describe the changes in the optical properties of a dye molecule by influence of the solvent characteristics. Solvatochromic shifts are governed by intermolecular interactions between solute-solvent that can be either electrostatic (non-specific interactions) or chemical (specific interactions). Due to the complexity of these interactions and absence of theoretical models that can explain the specific effects of solvent, different authors have introduced empirical parameters to building more reliable solvent polarity scales. Out of various polarity scales that have arisen from this need, those based on the effect of solvent polarity on the electronic excitation energy of indicator organic dyes are the most prevalent in literature. The use of empirical equations that correlate bathochromic (positive solvatochromism) and hypsochromic (negative solvatochromism) shifts of optical spectra of organic molecules with the polarity of solvent has become essential for understanding solute-solvent interactions. This review article presents main mathematical equations that use linear correlations between macroscopic and/or microscopic polarity functions of solvent with spectroscopic parameters of solute (dye) in construction of solvent polarity scales. In addition, main mathematical models that use solvatochromic shifts to estimate the dipole moment of ground and excited state are discussed.

Solvatochromism in SWCNTs suspended by conjugated polymers in organic solvents.

Despite the extensive utilization of carbon nanostructures as sensors, the factors that most affect their performance remain insufficiently understood. Many nanocarbon-based sensors are either processed in liquid environments or applied as liquid suspensions, which leads to solvatochromism, substantially influencing the underlying optical transitions. Most of the principles established so far apply only to nanocarbon species dispersed in polar environments by common surfactants, so the reported findings are not universal. For instance, they cannot describe the behavior of single-walled carbon nanotubes (SWCNTs) suspended in organic solvents by conjugated polymers (CPs), which have recently received considerable attention from the scientific community. Our research responds to this lack of knowledge and provides a thorough understanding of this topic by investigating SWCNT nanocomposites based on polyfluorenes and their co-polymers. A careful selection of an autonomous reference and precise spectral analysis allowed us to measure absolute solvatochromic shifts, by using which we identified and derived the underlying relationships affecting the optical properties of the material. Elucidation of the complex interactions between the polymer structure, SWCNT chirality, and solvent characteristics gave rise to the formulation of a revised mechanism of solvatochromism in SWCNTs. The in-depth experimental and theoretical examination revealed that in the case of CP-solubilized SWCNTs, the solvatochromic shifts strictly depend on the assignment of individual chiral types to mods and families, which experience the strain exerted by the polymer chains in different ways.

Role of the solvent polarity on the optical and electronic characteristics of 1-iodoadamantane.

The natural absorbance caused by the chromophore and chemical behavior of 1-iodoadamantane is highly influenced by the polarity of different solvent environments. This gives rise to the solvatochromatic shifts in the optical absorption and electronic structure and the experimentally measured UV-vis absorption spectra show significant solvatochromic shifts with respect to the solvent polarity. The absorption shift for both σ to σ*and n to σ* electronic transitions are more dominant in polar solvents than in nonpolar solvents. To obtain a better understanding of the impact of solvent polarity on the 1-iodoadamantane at the molecular level, computational calculations were carried out through implicit solvation. According to this, changes in the HOMO and LUMO energies and electron density distributions of various solvent continuums demonstrate the influence of solvent polarity on the HOMO and LUMO energy levels of the chemical system. This also shows an increment in the HOMO-LUMO gap with respect to the polarity of the solvent.

TD-DFT calculations, dipole moments, and solvatochromic properties of 2-aminochromone-3-carboxaldehyde and its hydrazone derivatives.

2-Aminochromone-3-carboxaldehyde (ACC) and its hydrazones (ACMHCA and ACMNPHTCA) with semicarbazide hydrochloride and N-phenylthiosemicarbazide were synthesized and characterized by elemental analysis and spectral studies. The solvatochromic behavior of the title compounds in various solvents showed distinct bathochromic shifts on going from nonpolar to polar solvents, suggesting intramolecular-charge-transfer (ICT) solute-solvent interactions. The ground and excited state dipole moments of ACC, ACMHCA, and ACMNPHTCA were determined experimentally by the solvatochromic shift method using the Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet functions, and a microscopic Reichardt's solvent polarity parameter (ENT). All the investigated molecules showed a substantial increase in the dipole moment upon excitation to the emitting state. The experimental results were generally consistent with the values obtained by the TD-DFT, B3LYP/6-311G++(d,p) method. Molecular electrostatic potential (MEP) mapping and natural charge and natural bonding orbital (NBO) analysis were performed and the results were discussed. The 1H NMR chemical shifts of the prepared compounds were simulated by the gage independent atomic orbital (GIAO) method and compared with their experimental chemical shift values. The biological activity data were correlated with the frontier molecular orbitals. The photovoltaic behavior of the title compounds showed there was sufficient electron injection.

A red-emitting thiophene-modified BODIPY probe for fluorescence lifetime-based polarity imaging of lipid droplets in living cells.

Intracellular polarity in lipid droplets as well as other organelles may provide useful knowledge about various processes taking place in live cells. Therefore, small fluorophores capable of visualising polarity are undergoing rapid development. In this paper, we report new red-emitting polarity sensitive BODIPY probes that can distinguish between liquid-ordered and liquid-disordered phases and can internalise into lipid droplets of live cells. Our reported probes sense lipid environment not through solvatochromic shift of the fluorescence spectra but through the change in the fluorescence lifetime of their monoexponential decays. This makes them convenient for fluorescence lifetime imaging microscopy. The probes were synthesised by modifying viscosity-sensitive meso-phenyl BODIPY with electron-donating 2-thienyl moieties at the α- and β-positions, significantly red-shifting absorption and fluorescence spectra of the dyes and improving sensitivity to polarity, while suppressing viscosity dependence. Finally, a novel probe - BP OC16 TP2 was suitable for sensing polarity in lipid droplets of live MCF-7 human breast cancer cells. We demonstrated that different chemotherapeutics affected lipid droplet polarity differently: cisplatin had no effect on lipid droplet polarity, whereas paclitaxel, depending on its concentration, either decreased or increased lipid droplet polarity.

Effect of Hydroxyl Group on Photo-Physical Properties and Dipole Moments of Fluorescent Dyes: An Experimental and Computational Approach.

In this work, structurally similar, (E)-N'-(2-hydroxybenzylidene)-3,5-di-tert-butyl-2-hydroxybenzohydrazide (A) and (E)-N'-(2-4-dihydroxybenzylidene)-3,5-di-tert-butyl-2-hydroxybenzohydrazide (A-OH) dyes dissolved in general solvents have been studied to explore photo-physical properties, employing solvatochromic shift method, thereby determining their dipole moments in the ground (μg) and excited (μe) states. The molecule A shows a bathochromic shift of fluorescence emission maxima in aprotic solvents whereas a hypsochromic shift in protic solvents. Interestingly, A-OH follows a hypsochromic shift in both protic and aprotic solvents with increasing solvent polarity. The effect of hydroxyl substituent on UV-Visible absorption, fluorescence emission, and dipole moment of the titled organic molecules was explained. Theoretical methods such as Bilot-Kawski method for determination of μg and μe and Bakshiev, Kawski-Chamma-Viallet, Lippert-Mataga equations for μe, and Reichardt method for the difference between μg and μe were employed. It is observed that μe is higher than that of μg for both the molecules, and interestingly, upon substituting an additional hydroxyl group the value of μg has increased while μe is decreased. The DFT calculations have been performed to support experimental results by employing DFT/B3LYP/6-311G + (d) and TD-DFT/B3LYP/6-311G + (d) method using Gaussian09 software. The electrophilic and nucleophilic sites on the molecules were studied with the help of MEP. The NBO analysis results show that the interaction N24 (σ) → C22-O23 (π*) is found to be stronger in both the molecules with energy 68.90kJ/mol and the effect of hydroxyl group is also discussed on the basis of HOMO and LUMO.