Sekar Nagaiyan

• Ph D(Tech)
• Head of Department at Institute of Chemical Technology

The current research involves a computational examination of the anthrapyrazoles, anthraisoxazoles, and proposed anthraisothiazoles using density functional theory (DFT). Through this analysis, it was found that the heterocyclic cores exhibit significant chemical reactivity, serving as electron donor spots and active sites for potential electrophil...

Density functional theory (DFT) and time‐dependent DFT (TD‐DFT) were used to investigate the linear and nonlinear optical properties of 1‐substituted coumarins. The molecular electrostatic potential plot, frontier molecular orbitals, and natural bond order analysis were used to study charge transfer properties. The bandgap exhibited an inverse rela...

In this study, the density functional theory (DFT) method is used to theoretically investigate the nonlinear optical (NLO) properties of natural carbazoles. The selected carbazoles have significant NLO characteristics. Using the B3LYP/6‐311++G(d,p) and CAM‐B3LYP/6‐311++G(d,p) level theories, the linear optical absorption, HOMO‐LUMO energy gap, mole...

The efficacy of aniline and carbazole‐based sensitizers used in dye‐sensitized solar cells (DSSCs) is correlated with the trends in density functional theory (DFT) based charge transfer (CT) and non‐linear optical (NLO) properties since both DSSC and NLO properties highly rely on CT properties. The aniline‐based donors showed a higher degree of pla...

This review is about anthraquinone dyes. One of the advantages of organic NLOphores materials is the variety of chromophores explored for a wide range of potential applications in optoelectronics and biology. The second and third harmonic generations, as well as hyper‐Rayleigh scattering (HRS), the Z‐scan technique, degenerate four‐wave mixing (DFW...

Density functional theory (DFT) and time dependent DFT (TD‐DFT) techniques are used to explore six donor‐pi‐acceptor (D−A) type sensitizers that comprise coumarin as the donor unit and cyanoacrylic acid as the acceptor unit. It is examined how adding a spacer bridge like 3,4‐ethylenedioxythiophene (EDOT) affects the system. The introduction of EDOT...

The linear and non-linear optical properties of 6-donor and 7-donor substituted coumarins were compared using density functional theory (DFT) and time-dependent-DFT (TD-DFT). Charge transfer characteristics were investigated through natural bond order analysis, frontier molecular orbital, and molecular electrostatic po- tential plots. TD-DFT resu...

Anthrone- and aniline-based azo dyes (4a-4i) are synthesized and well characterized. These dyes are further applied to wool, nylon, polyester, and acrylic fabrics. Fastness properties, including light, wash, and rub for dyed fabrics, were studied and found to be better for polyester and nylon than wool and acrylic substrate. Better sublimation fast...

Xanthene dyes exhibit remarkable photophysical properties and photostability. Their ability to switch fluorescence on/off depending on the external environment makes them a promising candidate for imaging/sensing/tracking/labeling probes. However, their emission ≤600 nm and Stokes shift ∼34 nm restrict their use in biological applications. A well‐k...

Anthrone and benzothiazole based disperse azo dyes (5a–5e) are synthesized and well characterized. These dyes are further applied to nylon, polyester, and acrylic fabrics. Fastness properties, including light, wash, and rub for dyed fabrics, were studied and found to be better for polyester and nylon than the acrylic substrate. Better sublimation f...

The efficacy of dipyridyl and diphenylamine sensitizers in dye‐sensitized solar cells (DSSCs) is linked to trends in DFT‐based charge transfer and non‐linear optical (NLO) properties. We chose DFT and Time‐dependent‐DFT methods. The planarity is improved by replacing the phenyl ring at the donor site with a thiophene ring. Similarly, cyanoacetic ac...

Four donor‐pi‐acceptor (D‐π‐A) type sensitizers containing coumarin as the donor unit and cyanoacrylic acid as the acceptor unit are investigated using density functional theory (DFT) and time‐dependent‐DFT methods. The effect of introducing auxiliary acceptor like benzothiadiazole and spacer bridge like 3,4‐ethylenedioxythiophene (EDOT) is analyze...

Xanthene dyes are well known for their remarkable photophysical property, photostability, and ability to switch fluorescence on-off depending upon the external environment. Such intriguing traits find a wide number of applications, albeit their emission (≤600 nm) and stokes shifts (∼34 nm) limit their use in biological applications. A well-known ap...

Linear and nonlinear optical (NLO) properties of three ESIPT-rhodol derivatives, spirocyclic and open-forms of 10, 11, and 12 estimated by spectroscopic based mathematical calculations and compared with computed values by using density functional theory (DFT) calculations. The group of global and range-separated hybrid functionals were used for the...

Disperse Red 343((E)‐N‐(2‐((2,6‐dicyano‐4‐methylphenyl) diazenyl) ‐ 5 ‐ (diethylamino) phenyl)methanesulfonamide,1 a), Disperse Red177((E) ‐ methyl3‐((2‐cyanoethyl)(4‐((6‐nitrobenzo [d]thiazol‐2‐yl)diazenyl) phenyl) amino) propanoate,1 b), Disperse Blue 165((E) ‐ N ‐ (2 ‐ ((2,6 ‐ dicyano ‐ 4 ‐nitrophenyl)diazenyl)‐5‐ (diethylamino) phenyl) acetamid...

Excited state intramolecular proton transfer (ESIPT) core containing, two series of benzothiazole and benzimidazole based fluorescent acid azo dyes were synthesized. These dyes analyzed and confirmed by ¹H NMR, ¹³C NMR, FT-IR and elemental analysis. Spectral characteristics of these dyes studied in different polarity solvents showed Stokes shift 28...

Dyes having coumarin core which absorbs and emits in deep-red to NIR region have become incredibly valuable due to their essential role in biology, DSSC, NLO materials, and LASER dyes. More precisely, these dyes have found application in biological studies since deep-red, and near-infrared radiation allows deeper photon penetration in tissues, redu...

Water soluble fluorescent acid azo dyes with benzimidazole and benzothiazole component having excited state intramolecular proton transfer (ESIPT) core were synthesized by diazo coupling. The structure of the dyes were analysed and confirmed by Fourier Transform Infrared – spectroscopy (FT-IR), elemental analysis, ¹H NMR and ¹³C NMR analysis. Absor...

Microwave assisted hydro-distillation (MAHD) and conventional hydro-distillation (HD) techniques were compared in the extraction of essential oils from Amomum subulatum seeds. The time required for MAHD method (70 min) is lesser than that for HD method (4 hr). There is a slight increase in the yield of extracted oil in MAHD method (3.35%) compared...

This review gathers the hyperpolarizabilities of monomeric azo dyes studied by various analytical techniques - electric-field-induced second-harmonic generation (EFISHG), hyper-Rayleigh scattering (HRS), Z-scan technique, solvatochromic method, and density functional theory (DFT). Dyes are sub-classified according to their structural characteristic...

We report four azo dyes and their positional isomers having a benzothiazole-pyridone core. Selected heterocyclic emissive azo dyes in this work are analysed for their non-linear optical (NLO) properties. Non-linear absorptive coefficient (β), non-linear refractive index (ƞ2), third-order NLO susceptibility (χ3), and optical limiting (OL) in differe...

Density functional theory (DFT) and time-dependent DFT computations were employed to examine linear and nonlinear optical (NLO) characteristics of (E)-4-((1,1-dioxido-3-oxobenzo[b]thiophen-2(3H)-ylidene) ethyl)-1-phenyl-1H-pyrazol-5(4H)-one derived styryl dyes. NLO properties were computed using the two different global hybrid functionals B3LYP, BH...

The Z-scan and DFT techniques were explored to investigate the non-linear optical properties of anthraquinone fused imidazole-based D-π-A dyes. With the help of UV–visible spectral analysis, pH study, CV analysis, HOMO-LUMO interaction, MEP plots, and quinoidal character the influence of intramolecular charge transfer characteristics and H-bonding...

Julolidine or TPA donor and tricyanofuran acceptor systems are selected to assess the ‘ground state molecular aspects’ and NLO properties of dyes. Six different functionals with five solvents are used to compute vertical excitations and hyperpolarizabilities. The trends in vertical excitations seen in B3LYP functional are comparable with experiment...

We have designed ten molecules having “donor‐π‐acceptor system”. Coumarin and carbazole connected to tricyanofuran acceptor unit are selected to study their “ground state” structural and NLO properties. Six functionals with five solvents are used to obtain vertical excitation and hyperpolarizabilities. “Amplitude of sine‐shaped potential” decreases...

Synthesis of a parallel series of hydrophobic azo dyes (4-hydroxy benzophenone and corresponding 4-methoxy benzophenone series) and a comprehensive systematic spectroscopic study in solvents of varying polarity and viscosity is presented. This includes glycerol-dimethylsulfoxide, toluene–polyethylene glycol 400 and toluene–paraffin oil viscous mixt...

Functional group and position isomers of azo and azomethine were selected to investigate their effect on linear and NLO properties. The azo and azomethine analogs show absorption maxima in the range 460–500 nm and 375–435 nm respectively. They are emissive in green, orange to the deep red region with a large Stokes shift of 100–200 nm. When we comp...

In this chapter mono, di, tri and tetraaza substituted phenanthrene derivatives have been investigated computationally with B3LYP/6-31 + G(d,p) level of theory. Substitution of carbon atom of the main structure with nitrogen obviously disturbs the aromaticity, indeed it decreases it. Thus, the idea of regaining of the aromaticity back by using elec...

Density functional theory (DFT) derived global reactivity descriptor, i. e. electrophilicity index, was used to reveal that photostability of the azo dyes. Light fastness property of azo dyes increases with strong electron withdrawing substituents at the ortho position of azo group. Molecular electrostatic potential (MEP) plot were used to identify...

We have explored detailed linear and nonlinear optical properties of push-pull systems bearing thienothiophene and dithienothiophene spacers. By using density functional theory (DFT), frequency-dependent strategies were applied to examine the polarizability ([Formula: see text] and hyperpolarizability ([Formula: see text] and [Formula: see text]. T...

Microwave-assisted hydrodistillation and conventional hydrodistillation (MAHD and HD) were used for a comparative study of extraction Callistemon citrinus Skeels leaf essential oils. The time required for a MAHD method is 75 minutes that for HD method is 3.5 hours, so MAHD requires lesser time. The increases in yield of extracted oil by MAHD (0.84%...

D-π-A chromophore derived coumarins are studied using “DFT and TD-DFT” to compute vertical excitation as well as NLO properties using “global hybrid” (GH) functionals B3LYP and BHandHLYP and “range separated hybrid” (RSH) functionals CAM B3LY’, wB97, wB97X, and wB97XD with basis set 6–311++G(d,p) and “correlation consistence polarized valence doubl...

The static and dynamic NLO properties of Anthraquinone based (D-π-A) dyes are determined by using the Density Functional Theory in ten different functionals. Five global hybrids and five long-range corrected hybrid functionals used based on Hartree-fork exchange contribution. The investigation of vertical excitation is also performed in the equival...

Deep red emitting dicyanovinylene isophorone based dyes are synthesized and studied for photophysical properties, viscosity sensitivity, and DFT. The dyes consist of Carbazole and Triphenylamine donor and thiophene spacer together with one auxiliary accepter, –CN leads to deep red emission towards the NIR region (∼600−700 nm) in polar solvent media...

This article is comprised of designing and synthesis of three coumarin-based donors (D)-π-azo-acceptor (A) colorants with -COOH and -SO3H anchoring groups for application in dye-sensitized solar cell (DSSC). Prototype DSSC devices were prepared with these colorants as sensitizers and were characterized through IV and EIS measurements to explore the...

In this review, we have explored the synthetic strategies adopted for designing the hydroxybenzazoles (imidazole, oxazole, and thiazole) i. e. HBX derivatives which show emission in red and NIR region. Further, we have examined the effect of different substituents i. e. either directly attached or with extended conjugation on a phenolic ring/ pheny...

To investigate the effect of substituents in azo dyes on their nonlinear optical properties, four azo dyes were synthesized using ethyl‐3‐hydroxy‐2‐naphthoate as a coupler and characterized. The polarizability (α) and hyperpolarizability (β and γ) constants were determined by using solvatochromic and computational method. A group of global hybrid a...

Positional isomers of benzothiazole-pyridone and benzothiazole-pyrazole containing disperse azo dyes are reported. These heterocyclic azo dyes are decorated with 'separate ESIPT core' and show emission in seven solvents of different polarity. After application on polyester fabric, "very good to excellent" light and washing fastness properties were...

Nonlinear optical properties of 4-(diethylamino)-7-imino-7H-benzo[4,5]imidazo[1,2-a]chromeno[3,2-c]pyridine-6-carbonitrile (C.I. Disperse Red 277), a red fluorescent dye estimated spectroscopically are found in good agreement with the values estimated with density functional theory based on ab initio method using the global hybrid (GH) and range se...

The non‐linear and linear optical properties of 2‐napthol based four monoazo dyes were examined by computational and Z‐scan methods. Time‐dependent (TD)‐density functional theory (DFT) computations were used to evaluate the linear polarizability (α), first‐order hyperpolarizability (β) and second‐order hyperpolarizability (γ) using global hybrid an...

Orthogonally dimeric meso attached dipyrromethene dyes are examined using computational tools with help of pure, RSH and GH functionals using 6-311++G(d,p) basis set for their steady-state absorption, nonlinear optical characteristics, and singlet-triplet distribution. The vertical excitations of the corresponding oscillator strengths are determine...

The NLO characteristics of anthraquinone imidazole-fused D-π-A dyes were investigated by Z-scan and density functional theory (DFT) methods. The electronic and photophysical studies i.e. the intramolecular charge transfer (ICT) characteristics were demonstrated by UV-visible analysis, cyclic voltammetry (CV) study, frontier molecular orbital (FMO),...

(Z)-2-(2-(4-(Dihexylamino)-2-methylbenzylidene)-1,1-dioxidobenzo[b]thiophen-3(2H)ylidene)malononitrile (C.I.Disperse Blue 354) and (E)-N-(2-((2-bromo-6-cyano-4-nitrophenyl)diazenyl)-5-(diethylamino)phenyl)propionamide (C.I.Disperse Blue 183) are investigated for nonlinear optical (NLO) properties using Density Functional Theory (DFT) and Z-scan tec...

Three novel hydroxyl substituted and triphenylamine sidearm coumarin decorated molecules were prepared to examine the effect of adjacent hydroxyl substituent as well as coumarin units on the photophysical linear and nonlinear optical properties. Both hydroxyl function adjacent to the phenyl ring and extra coumarin unit is attributed to the red shif...

This article reports design and synthesis of three new fluorophores (5 a‐c) with the donor‐π‐acceptor‐π‐donor motif, where dicyano vinylene group is the central acceptor, N‐ethyl carbazole group is a fixed donor and varying the N‐substituted secondary donors so as to study their photophysical behavior. Based on the systematic photophysical and theo...

Positional isomers of “benzothiazoles-pyrazole based azo dyes containing separate with ESIPT core” are analyzed for their “linear and non-linear optical (NLO)” properties. Dyes are emissive in ACN having Stokes shift in the range of 75 nm. Spectroscopic properties are further utilized to calculate band gap by CV. Band gap obtained by DFT and cyclic...

To study the effect of additional hydroxy-imidazole unit on the solvatochromic linear, and non-linear optical properties, three donor-pi-acceptor NLOphoric triphenylamine-imidazole based compounds were synthesized, and characterized. The photophysical characteristics of the synthesized compounds were examined in series of solvents. The solvatochrom...

NLOphoric D‐π‐A‐π‐D coumarin chalcone 5 and their BF2 complex 6 were designed, synthesized and characterized through Mass,¹³C‐NMR, and ¹H‐NMR analysis. Their Photophysical properties are extensively studied in solvents of different polarity. On BF2 complexation of coumarin chalcone shows highly red shift in absorption and emission spectra compared...

3‐Azabenzanthrone based chromophores are investigated to study the effect of different substituents on optical and “non‐linear optical (NLO)” properties by means of density functional theory (DFT) with global hybrid functionals (GHs) ‐ B3LYP and BHandHLYP, range separated hybrid functionals (RSHs) CAM−B3LYP, wB97, wB97X, wB97XD and the basis sets 6...

The structural, electronic, intramolecular charge transfer (ICT) and nonlinear optical (NLO) properties of the donor-π-acceptor (D-π-A) azo linked dyes bearing coumarin thiophene bridge with different acceptors were inspected by Z-scan and DFT methods. The dye 3a exhibits bathochromic absorption maxima (649 and 650 nm) in the near IR region in DMF...

Monoazo colorants with separate inbuilt ESIPT core were selected to examine the influence of azo group para to the hydroxyl group of ESIPT core and their effect on their spectral properties. They displayed absorption maxima in the visible region around 480–493 nm. 6a exhibited a broad peak along with a bathochromic shift of 40/90 nm in the solvents...

Three novel triphenylamine based fluorescent molecular rotors (FMRs) are designed and synthesized to study the effect of auxiliary methoxy substituent on aggregation induced emission (AIE) and viscosity sensitivity. Instead of elongated, short conjugated dicyanovinyl derivatives are preferred for the improved AIE and viscosity sensitivity propertie...

A series of seven new fluorescent brighteners 5-(1H-benzo[d]oxazole, thiazole, imidazole-2-yl)-2-methyl quinazolin-4-ol were synthesized by chemical reaction of 2-Methyl-4-oxo-3,4-dihydroquinazoline-5- carboxylic acid and derivatives of 2-aminophenol/2- minothiophenol/1,2-phenylenediamine attributes to its computational and experimental comparison....

Three rhodol derivatives, namely spirolactamized phenanthrene-imidazole, diphenyl-imidazole and benzothiazole substituted N, N-diethylamine rhodols were designed, synthesized and characterized. Their photophysical properties were studied in spirocyclic and open form from non-polar to polar solvents. The spirocyclic form exhibited larger Stokes shif...

Organic dyes, both in solution phase and in immobilized condition, are useful tools for optical detection. Studies have shown that spectral property of dyes in solution are different from that in the immobilized state. In this work, we have studied the optical properties of dyes in solution as well as in immobilized state with three categories of d...

Analogs of 2-[(2Z)-2-[[4-(dihexylamino)-2-methylphenyl]methylidene]-1,1-dioxo-1-benzothiophen-3-ylidene]propanedinitrile (Foron blue SR, Disperse Blue 354) are studied in terms of photophysical, structural aspects and its nonlinear optical properties evaluated by using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD...

3-Ethoxy-N,N-diethylaniline substituted aza-BODIPY dye (7) was designed and synthesized that could recognize Cu (II) ions through sequential binding interactions. The visible changes in the absorption and enhancement in fluorescence intensity with the addition of Cu (II) ions makes this dye as a selective and sensitive probe for on-site visual dete...

Disperse azo dyes are synthesized and characterized by 1H NMR, 13C NMR, LC-MS, Elemental analysis, UV-visible, and fluorescence spectroscopy methods. The azo dyes show absorption maxima in the range of 460-493 nm. Dye with benzothiazole moiety i.e. VM7a and VM8a show a bathochromic shift in absorption maxima of 90 and 26 nm respectively in a polar...

Novel Donor (D)-π-Acceptor (A) NLOphoric triphenylamine-imidazole based dye 9 was designed, synthesized, and confirmed by Mass, 13C NMR, and 1H NMR analysis. Photophysical properties of 9 were studied in solvents of different polarities and compared with analogues compounds 7 and 8. Phenonthroline acceptor based dye 9 shows highly bathochromic shif...

We have designed and synthesized two dye molecules viz. MMR1 ((E)‐2‐cyano‐3‐(5‐((E)‐1‐cyano‐2‐(4′‐(dimethylamino)‐[1,1′‐biphenyl]‐4‐yl)vinyl)thiophen‐2‐yl)acrylic acid) and MMR2 (2‐((Z)‐5‐((5‐((E)‐1‐cyano‐2‐(4′‐(dimethylamino)‐[1,1′‐biphenyl]‐4‐yl)vinyl)thiophen‐2‐yl)methylene)‐4‐oxo‐2‐thioxothiazolidin‐3‐yl)acetic acid) with D‐π‐A’‐π‐A frameworks....

Five azo dyes with ESIPT unit were used to study their application properties. These dyes were used for coloration on polyester (PET), acrylic (AC) and nylon (NY) fabrics. The various properties of fastness, UV blocking, UV protection properties were investigated. Elecrophilicity index was calculated for comparing with the trends in lightfastness p...

Four new D-π-A-π-D hybrid dyes containing coumarin as a major donor (4a-b and 5a-b) together with carbazole and triphenylamine as auxiliary donor having dicyanovinylene as a common acceptor are synthesized and studied in terms of photophysical, charge transfer, and non-linear optical properties. Optical properties of hybrid dyes considerably shifte...

In a sequential study of rigidification of donating unit on its charge transfer towards accepting a coumarin unit, four donor-acceptor triphenylamine and N-phenyl carbazole based coumarin dyes were synthesized and characterized. The dyes exhibit positive solvatochromism which is well supported by linear as well as multilinear regression analysis. T...

Six new azo clubbed benzothiazole dyes were synthesized by diazotization reaction. These six novel compounds were characterized using ¹ H NMR, FTIR, UV–Visible, fluorescence spectroscopy, LC-MS, and elemental analysis. The in-vitro antimicrobial screening studies were performed using popular REMA assay method on “gram-positive” (“Staphylococcus aur...

Three new carbazole functionalized A-π-D-π-A extended chromophores 4a, 4b and 4c comprising of different chemical functional groups on C=C bond with the assistance of chlorovinylene group in π-conjugation are synthesized and investigated spectroscopically. We have investigated the effect of different electron acceptors - carboxycyanomethylene, dicy...

Four new metal free organic Schiff bases employing N‐hexyl/N‐phenyl carbazole moiety as a donor, 1‐chlorobuta‐1,3‐diene as a π‐bridge and 4‐amino salicylic acid as an anchor, are designed, synthesized and investigated as photosensitizers in the dye‐sensitized solar cell (DSSC). We have studied the combined effect of the introduction of electronegat...

Quinoxaline derivative QY 54 A, an analog of commercially available C.I. (Colour index) Disperse Yellow 54 (quinoline derivative) is synthesized and confirmed by ¹H, ¹³C NMR, LC–MS, and CHN analysis. It is emissive (512 nm) with a quantum yield (ϕF) =0.34. The electrochemical properties of both the dyes were investigated using cyclic voltammetry (C...

Report is about the synthesized new range of oxadiazole substituted quinazoline and studied its electronic distribution to attribute fluorescent properties. B3LYP Density Functional Theory (DFT) computational optimization was studied to observe the effect of electron donor and acceptor substituent's on photophysical properties, electronic state and...

OPHY(BPY) and BODIPY (BDY) dye bearing benzyl group (Bn) at 4,4′ and 2,6 position respectivelywere synthesized and characterized. The fluorescence decaymeasurementswere performedwhich reveal that benzyl BOPHY (Bn-BPY) has shorter fluorescence lifetime compared to benzyl BODIPY (Bn-BDY). The difference in transition dipole moment is found to be 6.93...

2-(Naphthalen-2-yl)benzo[d]thiazolemesofused dipyrromethene boron difluoride dyes are synthesised and theirlinear and non-linear optical properties are studied. The third order nonlinear susceptibility (χ3) value obtainedfrom the Z-scan experiment is 11.21 × 10−13and 13.30 × 10−13esu. The global hybrid (B3LYP and BHHLYP)and range-separated hybrid (...

Four novel D-π-A extended styryl colorants containing carbazole unit were designed and modified synthetically to evaluate the effect of various acceptors on ICT (intramolecular charge transfer) characteristics and to investigate the effect of incorporation of an additional π-bond along with the assistance of electron withdrawing chlorine group in t...

Five (MA1-MA5) hemicyanine based sensitizer having N, N-diethyl aniline as a primary donor and hydroxy or alkoxy as an auxiliary donor have been synthesized to establish a correlation between amphiphilic nature of the sensitizer and charge recombination. A strong electron withdrawing 3-(carboxymethyl)-2-methylbenzo[d]thiazol-3-ium bromide has been...