Hush Analysis Research Articles

Spectroscopic Recognition of Metal Ions and Non-Linear Optical (NLO) Properties of Some Fluorinated Poly(1,3,4-Oxadiazole-Ether)s

In this paper, we examined the sensing ability of some fluorinated 1,3,4-oxadiazole-containing assemblies toward various metal ions and their nonlinear optical (NLO) properties. The changes in the spectral characteristics of these compounds in the existence of Mg2+, Mn2+, Ni2+, Cd2+, Zn2+, Co2+, Cu2+, Hg2+, Sn2+, and Ag+ metal ions were performed, and they were found to be selective and more sensitive toward the addition of Ag+, Co2+, and Cu2+ ions (new bands appeared). Instead, spectral changes in the presence of Mg2+, Mn2+, Ni2+, Cd2+, Zn2+, Hg2+, and Sn2+ were not significant, so we did not evaluate the corresponding binding parameters. Therefore, all of these compounds were found to be selective and sensitive to Ag+, Co2+, and Cu2+ ions. Furthermore, the first-order polarizability (αCT), the first-order hyperpolarizability (βCT), and the second-order hyperpolarizability (γCT) were evaluated using the solvatochromic approach, and the intramolecular charge transfer (ICT) characteristics were investigated using a generalized Mulliken–Hush (GMH) analysis.

Evaluation of Through‐Space Electronic Coupling in the Cofacially Aligned π‐Stacked Organic Mixed‐Valence System

A new π‐stacked compound, 1,8‐bis(2′,5′‐dimethoxy‐4′‐methyl‐[1,1′‐biphenyl]‐4‐yl)naphthalene (1) has been synthesized and characterized as a precursor molecule of monocationic mixed‐valence system (MVS). Cyclic and differential pulse voltammograms reveal that the ΔE°ox value between two sequential oxidation potentials is 163 mV. The three‐dimensional geometries of 1, 1•+, and 12+ were obtained via using density functional theory (DFT) calculations with a range‐separated hybrid functional and dispersion corrections (LC‐wPBE‐D3). Two dimethoxytoluene redox centers were aligned in parallel with van der Waals interplanar distances (3.50–3.70 Å). The electronic coupling in this MVS was evaluated by two different approaches: (1) Mulliken–Hush analysis of intervalence charge transfer (IVCT) band obtained from the spectroelectrochemical method, and (2) partial charge distribution analysis of quinonoidal distortion of D•+/D centers obtained from theoretical DFT calculations. The H12 were 2055 and 1903 cm−1 by (1) and (2), respectively. This work suggests that the pure through‐space electronic coupling can be large when two aromatic redox centers are properly aligned.

Deep Red emitting dicyanovinylene isophorone based chromophores: Combined synthesis, optical properties, viscosity sensitivity, and DFT studies

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. All dyes show good emission solvatochromism with an increase in solvent polarity. The dyes show intramolecular (ICT) as well as “Twisted Intramolecular Charge Transfer (TICT)” which is reinforced by Lippert Mataga, MacRae, Weller, and Rettig plots. Viscosity induced emission enhancement study in ethanol/polyethylene glycol (PEG 400) system shows 4.34–4.85 folds increases emission intensity. ICT is supported by Frontier Molecular Orbital (FMO) diagram and bandgap energy. The observed experimental findings are also correlated with the computed values using “Density Functional Theory (DFT)”. The magnitudes of “first order hyperpolarizability”(β0) are 500−1000 × 10−30.e.s.u. while those of the “second order hyperpolarizability”(γ) are 3000−8300 × 10-36 e.s.u. Hence they can act as very good NLOphores. Mulliken Hush analysis and Natural Bond Orbital (NBO) analysis were used to support charge transfer characteristics.

Yellow-red emitting, methoxy substituted triphenylamine-based styryl derivatives: Synthesis, photophysical properties, viscosity sensitivity, aggregation induced emission, NLO properties, and DFT study

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 properties. The sensitivity study of fluorescence emission towards viscosity and polarity of organic solvents was investigated by UV visible solvatochromism study, while AIE study was performed in DMF-water mixture of solvents. All the compounds were well characterized by 1H and 13C NMR, mass spectra IR as well as elemental analysis. They exhibited very good solid state emission between 544–620 nm. High values for their first and second order hyperpolarizability (378–1755 х10^-36 e.s.u) are observed. ‘Two photon absorption cross sections’ are in the range of 168–229 GM for 3. Effective charge transfer is elucidated using Mulliken Hush analysis.

Red emitting coumarin based 4, 6-disubstituted-3-cyano-2-pyridones dyes – Synthesis, solvatochromism, linear and non-linear optical properties

New coumarin fluorescent based D-π-A-π-D dyes are synthesized and studied for their optical properties. Their show absorption and emission respectively are in the range of 471–504 nm and 506–550 nm. Viscosity induced emission intensity increase is examined with 0–100% PEG-400 in ethanol MLK 4 is good FMR as compared to the MLK 1–3 due to the presence of extra-π-conjugation. FMO analysis and Generalized Mulliken Hush analysis show a strong interaction of molecular charge transfer characteristics. The first (α), second (β) and third (γ) order polarizability of MLK 1–4 are calculated by the solvatochromic technique and corroborated by DFT calculations using CAM-B3LYP/6-31G(d) method. The outcomes found by solvatochromic technique are compared theoretically with DFT using B3LYP/6-31G(d) and CAM-B3LYP/6-31G(d) methods. These methods reveal that, CAM-B3LYP/6-31G(d) carry out for calculating α, β, γ. Photophysical data was also applied to establish the ground and excited state dipole moment ratio using Bakhshiev, Bilot-Kawski, and Liptay functions. Liptay function shows better correlations than the other two functions for all dyes.

Synthesis, photophysical, viscosity and DFT study of solid state fluorescent molecular rotors

Four novel Fluorescent Molecular Rotors (FMR) (1, 2, 3, 4) comprising carbazole, triphenylamine, phenothiazine, diethylaniline as donating groups and cyanoformyl vinylene as an accepting group are synthesized and characterized by NMR. They show emission in the solid state in the range of 581–651 nm. The viscosity sensitivity of emission was investigated 3.1–3.4 fold increase in emission intensity was observed in a mixture of polar protic ethanol and polyethyleneglycol 400 mixture. The experimental results are well in correlation with those of Density Functional Theory (DFT) computations. Compounds show higher values of dipole moment, linear polarizability values ranging from 49 to 59 × 10^−24 e.s.u., first order hyperpolarizability ranging from 77 to 250 × 10^-30 e.s.u. and second order hyperpolarizability ranging between 105–695 × 10^-30 e.s.u. suggest that the compounds show good Nonlinear Optical (NLO) property. The two photon absorption cross sections are found in the range 50–150 GM, which is further elucidated using Mulliken Hush analysis for analyzing effective charge transfer in the present compounds.

Fluorescent 7-Substituted Coumarin Dyes: Solvatochromism and NLO Studies

The effect of three substituents N,N-diethylamine, carbazole and diphenylamine at the 7 position of coumarin on linear and nonlinear optical properties are studied using absorption and emission solvatochromism, and DFT. By varying the substituent 53nm red shift is achieved in emission. The polarity plots with regression close to unity revealed good charge transfer in the system. Solvent polarizability and dipolarity are mainly responsible for solvatochromic shift as proved by multilinear regression analysis. General Mulliken Hush analysis shows diphenylamine substituent leads to more charge separation in compound 6c. The hyperpolarizabilities are evaluated by quantum mechanical calculations. Structure of the compounds are optimized at B3LYP/6-31G(d) level and NLO computations are done using range separated hybrid functionals with large basis sets. Second order hyperpolarizability (γ) found 589.27 × 10-36, 841.29 × 10-36 and 1043.00 × 10-36 e.s.u for the compounds 6a, 6b and 6c respectively.

Fluorescent carbazole based pyridone dyes – Synthesis, solvatochromism, linear and nonlinear optical properties

Carbazole based pyridone dyes are investigated for their non-linear optical (NLO) properties. They exhibit positive solvatochromism and charge transfer character with a high fluorescence quantum yield which encouraged us to study their NLO characteristics. Photophysical properties of dyes in different solvents are evaluated and correlated with computational optical absorption and fluorescence emission using global hybrid (B3LYP) and long range separated functional (CAM-B3LYP) with 6–31G(d) basic set. Frontier Molecular Orbital analysis and Generalised Mulliken Hush analysis reveal a strong intramolecular molecular charge transfer character in these dyes. DFT and TD-DFT are performed to understand the electronic and photophysical properties of dyes. The resultant decrease in the HOMO-LUMO energy gap is responsible for bathochromic shift. Large enhancement in the non-linear optical properties are seen for these dyes than urea confirming their use in non-linear optical materials. The MEP analysis reveals the sites for electrophilic and nucleophilic attack in the dye. The experimental data are in good agreement with those obtained by computation (DFT) method. Fundamental limiting values of β, γ for dyes are observed within the estimated limits.

Triphenylamine Derived 3-Acetyl and 3-Benzothiazolyl Bis and Tris Coumarins: Synthesis, Photophysical and DFT Assisted Hyperpolarizability Study

Triphenylamine derived bis- and tris-branched donor-pi-acceptor coumarins with acetyl and benzothiazolyl acceptors are studied for their linear and nonlinear optical properties that originate from their photophysical and molecular structure. Plots of solvent polarities versus the Stokes shift, frontier molecular orbital analysis and Generalised Mulliken Hush analysis have established their strong charge transfer character supported by the strong emission solvatochromism of these chromophores. On the basis of excited state intramolecular charge transfer, the first-, second- and third-order polarizability of these dyes are determined by a solvatochromic method and supported by density functional theory calculations using CAM-B3LYP/6-31g(d). Compared to the acetyl group, the benzothiazolyl group is a strong acceptor, and its corresponding derivatives show enhanced absorption, emission maxima and non-linear optical response. Bond length alternation and bond order alternation analysis reveals that these chromophores approach the cyanine-like framework which is responsible for maximum perturbation to produce high nonlinear optical response. Third order nonlinear susceptibility for dyes 1 and 2 is determined by Z-scan measurement. All of these methods are used to determine the nonlinear optical properties, and thermogravimetric analysis suggests that these chromophores are thermally robust and efficient nonlinear optical materials.

Diferrocenes Bridged by a Geminal Diethynylethene Scaffold with Varying Pendant Substituents: Electronic Interactions in Cross-Conjugated System

A series of geminal diethynylethene (gem-DEE) bridged diferrocenyl compounds with varying pendant substituents at the side chain, including xanthene, thioxanthene, dibenzo[a,d]cycloheptene, and fluorene, is reported with the aim of exploring electronic interactions in the cross-conjugated system. The compounds 9-[bis(ferrocenylethynyl)methylene]-9H-xanthene (1), 9-[bis(ferrocenylethynyl)methylene]-9H-thioxanthene (2), 5-[bis(ferrocenylethynyl)methylene]-5H-dibenzo[a,d]cycloheptene (3), and 9-[bis(ferrocenylethynyl)methylene]-9H-fluorene (4) were synthesized and characterized by using spectroscopic methods and single-crystal X-ray diffraction analyses. Electrochemical measurements using the weakly coordinating electrolyte Na[B{C6H3(3,5-CF3)2}4] reveal the moderate electronic coupling between the ferrocenyl (Fc) termini. Hush analysis of the intervalence charge-transfer (IVCT) bands for the monocation species is suggestive of the weakly coupled Robin–Day class II mixed-valence compounds. DFT and TDDFT calcu...

Triphenylamine derived coumarin chalcones and their red emitting OBO difluoride complexes: Synthesis, photophysical and NLO property study

The auxiliary methoxy aided triphenylamine donors derived coumarin chalcones and their OBO complexes with branched donor-pi-acceptor systems are synthesized and characterized. Their photophysical properties are extensively studied in solvents of different polarity. They show strong emission solvatochromism and have quantum yields up to 0.87. The BF2-complexation of coumarin chalcones enhanced the quantum efficiency by approximately 1.4 times compared to the uncomplexed chalcones. Frontier molecular orbital analysis and Generalised Mulliken Hush analysis revealed a strong intramolecular charge transfer character of these chromophores. The first, second and third order polarizability of these chromophores are evaluated by the solvatochromic method and supported by Density Functional Theory calculations using CAM-B3LYP/6-31g(d) method. The third order nonlinear optical susceptibilities of these chromophores obtained by Z-scan analysis showed very less values of the imaginary part. Replacement of N-ethyl donors by aryl amine groups provided branched push-pull systems with enhanced thermal stability and nonlinear optical response.

NLOphoric multichromophoric auxiliary methoxy aided triphenylamine D-π-A chromophores – Spectroscopic and computational studies

Molecules containing methoxy supported triphenylamine as strong electron-donor and dicyanovinyl as electron-acceptor groups interacting via isophorone as a configurationally locked polyene π-conjugated bridge are studied for their nonlinear optical properties. The photophysical study of examined chromophores in non-polar and polar solvents suggest that they exhibit strong emission solvatochromism and significant charge transfer characteristics supported by Lippert-Mataga plots and Generalised Mulliken Hush analysis. Linear and nonlinear optical properties as well as electronic properties measured by spectroscopic methods and cyclic voltametry and supported by DFT calculation were used to elucidate the structure property relationships. All three chromophores exhibit very high thermal stabilities with the decomposition temperatures higher than 340°C. The vibrational motions play very important role in determining the overall NLO response styryl chromophores which was established by DFT study. Dye 3 with maximum nonlinear optical susceptibility among three D-π-A systems proves that the multibranched push-pull chromophores exhibit a higher third order nonlinear susceptibility and justifies the design strategy.

Investigation of NLO Properties of Fluorescent BORICO Dyes: a Comprehensive Experimental and Theoretical Approach.

BORICO dyes with N, N-diethyl as a strong donor and BF2 complexed iminocoumarin six member core as strong acceptor are investigated as an efficient non linear optical chromophores. Extended π-conjugation over iminocoumarin moiety is useful to make ICT character of BORICO dyes more significant and is established on the scale of Generalised Mulliken Hush analysis scale. Bond length alternation and bond order alternation values for three BORICO chromophores estimates the cyanine like framework for optimal non linear optical response. The frontier molecular orbital diagrams obtained from density functional theory calculations shows that there is charge transfer from donor to accepter as well as effective overlap between them making the basis for optimal NLO response of BORICO chromophores. The theoretical values of linear and non linear optical responses for three BORICO NLOphores obtained by using three different functionals B3LYP, CAMB3LYP and BHandHLYP with 6-311+g(d,p) basis set are quite consistent for the values of static dipole moment (μ), linear polarizability (α) and first hyperpolarizability (β). However in case of the γ values calculation, compare to the similar values obtained by CAMB3LYP and BHandHLYP functionals, B3LYP overestimates the same. The vibrational motions play decisive role in the overall non linear optical properties of BORICO chromophores.

Phenylpyran-fused coumarin novel derivatives: combined photophysical and theoretical study on structural modification for PET-inhibited ICT emission

Synthesis and characterizations of fluorescent derivatives of 2-amino-5-oxo-4, 5-dihydropyrano[3,2-c] chromene-3-carbonitrile class are presented. Detailed photophysical characterizations were performed with different substituents, which enabled getting into the details of structural modulation to understand and tune photophysical properties in this biologically important class of dyes. One of the synthesized nitro-substituted dye (4a) is non-fluorescent due to the photoinduced electron transfer (PET) process. PET is quenched and fluorescence emission is achieved by (i) reduction of the –NO2 group to the –NH2 group, (ii) substitution of –NO2 by different substituents (−N(Me)2, −Cl, and –OH groups), and (iii) aggregate formation of 4a in the tetrahydrofuran–water system resultant from aggregation-induced enhanced emission (AIEE). Synthesized derivatives having substituents (−NH2, −N(Me)2, −Cl and –OH group) are highly fluorescent. Synthesized dyes showed positive solvatochromism and enhanced photophysical properties as compared to parent dye 7-(diethylamino)-4-hydroxy-2H-chromen-2-one. ICT characteristics of dyes are in good correlation with solvent polarity plots, multilinear regression analysis of solvent parameters, and Mulliken–Hush analysis. Mathematically deduced global and local descriptors and computationally obtained molecular orbital calculations are supporting well the PET process in 4a and ICT process in other dyes.

Enhanced NLO response in BODIPY-coumarin hybrids: density functional theory approach

We have thoroughly investigated the first, second and third polarizability characteristics of four hybrid chromophores by spectroscopic and computational methods. B3LYP, CAMB3LYP and BHandHLYP functionals in combination with 6-311+G(d,p) basis set were used to evaluate the polarizability and hyperpolarizability characteristics of these chromophores. Generalized Mulliken Hush analysis and frontier molecular orbital electronic distribution images of chromophores obtained from Density functional theory computation has established the charge transfer characteristics of these hybrid chromophores. On the basis of charge transfer characteristic, these red absorbing and NIR emissive chromophores possess high nonlinear optical response. Comparison of isolated units with their analogous hybrid chromophores shows that fusion of coumarin with BODIPY enhances the nonlinear optical response. JCSC-D-17-00467 SYNOPSIS The NLO properties of coumarin-fused BODIPY hybrid chromophores were studied in details. Spectroscopic method gave rough estimation of polarizability and hyperpolarizability characteristics of four hybrid chromophores while computational approaches using three different hybrid functional, B3LYP, CAM-B3LYP and BHandHLYP in combination with 6-311+G(d,p) basis set, gave comparative estimation of these values. BLA/BOA calculations for ground and excited states suggested that the cyanine-type D- $$\pi $$ -A framework produces high NLO response. The hybrid molecules are proven to be the better performing NLOphores than the isolated coumarin or BODIPY units.

Substituent Modulation from ESIPT to ICT Emission in Benzoimidazolphenyl-methanones Derivatives: Synthesis, Photophysical and DFT Study

Design and synthesis of five new derivatives of benzophenone based imidazole dyes is presented. Synthesized dyes were well characterized by 1H NMR, 13C NMR, FT-IR and mass analysis. Dyes contain a secondary acceptor, ESIPT core and different donors forming (D-ESIPT core-A) as basic skeleton in order to study both ESIPT and ICT systematically in this same class of dyes. Dyes without a donor substituent showed ESIPT emission while dyes with a substituted strong donor showed intramolecular charge transfer (ICT) emission. Moreover emission properties of methoxy analogue dyes has been studied to further confirm non-ESIPT emission in dyes without donors and ICT emission in strong donor substituted dyes. All dyes exhibited long range emissions from 392 to 567 nm. Dyes exhibiting ESIPT emission showed negative solvatochromism while ICT emission exhibiting dyes shows positive solvatochromism. ICT and ESIPT characteristics are well correlated with polarity functions plots and Mulliken–Hush analysis. Experimental observations are well supported by TD–DFT and computed energies. The electrophilicity index has been calculated to get details of the stabilities of possible tautomers.

Spectroscopic, DFT and Z-scan supported investigation of dicyanoisophorone based push-pull NLOphoric styryl dyes

The dicyanoisophorone acceptor based NLOphores with Intramolecular Charge Transfer (ICT) character are newly synthesised, characterised and explored for linear and non linear optical (NLO) property investigation. Strong ICT character of these D-π-A styryl NLOphores is established with support of emission solvatochromism, polarity functions and Generalised Mulliken Hush (GMH) analysis. First, second and third order polarizability of these NLOphores is investigated by spectroscopic and TDDFT computational approach using CAM/B3LYP-6-311 + g (d, p) method. BLA and BOA values of these chromophores are evaluated from ground and excited state optimized geometries and found that the respective structures are approaching towards cyanine limit. Third order nonlinear susceptibility (X(3)) along with nonlinear absorption coefficient (β) and nonlinear refraction (n2) are evaluated for these NLOphores using Z-scan experiment. All four chromophores exhibit large polarization anisotropy (Δα), first order hyperpolarizability (β0), second order hyperpolarizability (γ) and third order nonlinear susceptibility (X(3)). TGA analysis proved these NLOphores are stable up to 320 °C and hence can be used in device fabrication.

Excited State Electron Transfer of All-Inorganic Heterobinuclear TiOMn2+ Chromophore Anchored on Silica Nanoparticle Surface

The oxo-bridged heterobinuclear chromophore TiOMn2+ has been covalently anchored onto a silica nanoparticle surface, allowing for the preparation of optically transparent solid state samples. Optical spectra of the material yield a broad metal-to-metal charge-transfer (MMCT) transition in the UV with a tail extending to 550 nm. Fitting the absorption band to a Gaussian curve gives a maximum at 44 610 (±230) cm–1 (587 (±20) M–1 cm–1) with a full width at half-maximum of 17 320 (±160) cm–1, and yields an electronic coupling constant, HABopt, of 4200 cm–1 by Hush analysis. Transient absorption measurements of transparent pressed pellets in vacuum yield a 2.43 (±0.20) μs lifetime at room temperature. The temperature dependence of the lifetime in the range of 10–40 °C gives an activation energy of 1.67 (±0.36) kcal/mol and pre-exponential factor A of 7.3 (±4.4) × 106 s–1. This temperature dependence results in an electronic coupling constant HABkin of less than 1 cm–1. The disparity between the large electroni...

Electron-Transfer Processes in 3,4-Diferrocenylpyrroles: Insight into a Missing Piece of the Polyferrocenyl-Containing Pyrroles Family

3,4-Diiodo-1-(triisopropylsilyl)-1H-pyrrole (1), 3,4-diferrocenyl-1-(triisopropylsilyl)-1H-pyrrole (2), and 3,4-diferrocenyl-1H-pyrrole (3) were prepared and characterized using spectroscopic methods and X-ray crystallography. UV–vis spectra of 2 and 3 were correlated with their density functional theory (DFT)-calculated electronic structures as well as theoretically predicted by the time-dependent (TD) DFT-calculations vertical excitation energies. Redox properties of 2 and 3 were investigated using cyclic voltammetry, differential pulse voltammetry, and spectroelectrochemical approaches. Ferrocene-centered oxidation processes in 2 and 3 were found to be separated by ∼180 and ∼300 mV in DCM/TBAP and DCM/(NBu4)[B(C6F5)4] systems, respectively. Stepwise spectroelectrochemical oxidation of 2 and 3 allowed us to obtain spectroscopic signatures of the mixed-valence [2]+ and [3]+ cations. Hush analysis of the intervalence charge-transfer band in [2]+ and [3]+ is suggestive of class II (in Robin and Day classif...

Efficient Electronic Communication of Two Ruthenium Centers through a Rigid Ditopic N‐Heterocyclic Carbene Linker

A ditopic benzobis(carbene) ligand precursor was prepared that contained a chelating pyridyl moiety to ensure co-planarity of the carbene ligand and the coordination plane of a bound octahedral metal center. Bimetallic ruthenium complexes comprising this ditopic ligand [L4Ru-C,N-bbi-C,N-RuL4] were obtained by a transmetalation methodology (C,N-bbi-C,N=benzobis(N-pyridyl-N'-methyl-imidazolylidene). The two metal centers are electronically decoupled when the ruthenium is in a pseudotetrahedral geometry imparted by a cymene spectator ligand (L4=[(cym)Cl]). Ligand exchange of the Cl(-)/cymene ligands for two bipyridine or four MeCN ligands induced a change of the coordination geometry to octahedral. As a consequence, the ruthenium centers, separated through space by more than 10 Å, become electronically coupled, which is evidenced by two distinctly different metal-centered oxidation processes that are separated by 134 mV (L4=[(bpy)2]; bpy=2,2'-bipyridine) and 244 mV (L4=[(MeCN)4]), respectively. Hush analysis of the intervalence charge-transfer bands in the mixed-valent species indicates substantial valence delocalization in both complexes (delocalization parameter Γ=0.41 and 0.37 in the bpy and MeCN complexes, respectively). Spectroelectrochemical measurements further indicated that the mixed-valent Ru(II)/Ru(III) species and the fully oxidized Ru(III)/Ru(III) complexes gradually decompose when bound to MeCN ligands, whereas the bpy spectators significantly enhance the stability. These results demonstrate the efficiency of carbenes and, in particular, of the bbi ligand scaffold for mediating electron transfer and for the fabrication of molecular redox switches. Moreover, the relevance of spectator ligands is emphasized for tailoring the degree of electronic communication through the benzobis(carbene) linker.