Dipole Moment Difference Research Articles

DFT molecular modeling investigation and optical properties characterization of CR-39 films

Abstract In this study, the structural and optical characteristics of CR-39 films were investigated both theoretically and experimentally. A number of parameters for the CR-39 structure were theoretically computed by the density functional theory (DFT) method at B3LYP/6–311 G (p, d) level of theory. FTIR and UV/Vis spectroscopy were used to determine the structure compositions and the optical parameters of the CR39 film, respectively. The computed and experimental findings show good concordance. It was found that the CR-39 compound’s total energy, dipole moment, and energy difference between the LUMO and HOMO were, respectively, −994.575 a.u., 2.772 Debye, and 7.045 eV. The MEP showed a progressive change in color, with blue signifying a low electron density and red denoting a high electron density linked to nucleophilic reactivity and electrophilic reactivity. Further, the positive charges on all hydrogen atoms, which range from 0.16506 to 0.22032 a.u., imply that they are acceptors. The positive H34 is strongly produced when electrons from the negatively charged C17 are taken up. Because they are donor atoms, part of the carbon atoms in the structure is negative, while the other atoms are positive. The highest electronegative atoms H23 and H24 were substituted, resulting in the extremely negative carbon atom C7 (−0.32436). According to the experimentally determined absorption coefficient and energy gap values, CR-39 films may find application in optoelectronic devices.

Theoretical investigation of benzodithiophene-based donor molecules in organic solar cells: from structural optimization to performance metrics.

Achieving high power conversion efficiency (PCE) remains a significant challenge in the advancement of organic solar cells (OSCs). In the field of organic photovoltaics (OPVs), considerable progress has been made in optimizing molecular structures to improve the PCE. However, innovative material design strategies specifically aimed at enhancing PCE are still needed. Here, we have designed BDTS-2DPP-based molecules and propose a molecular design approach to develop donor materials that can significantly improve the PCE of OSCs. Density functional theory (DFT) and time-dependent DFT (TD-DFT) methods have been adopted in both gas and solvent phases. Our newly designed molecule M1 shows the highest absorption value (λ max = 846 nm), highest electron reorganization energy (λ e = 0.18 eV), and the lowest energy gap (E g = 1.81 eV) among all the designed molecules. M1 molecule also exhibits the highest dipole moment in both gas (10.62 D) and solvent phase (13.62 D), and their ground and excited state dipole moment difference is also higher (μ e - μ g = 2.99 D), which enhances its separation to make it a suitable candidate for charge transfer between HOMO-LUMO (97%). Newly designed molecule M3 is observed to have the highest voltage when the current is zero (V oc = 1.15 V) highest PCE value (21.90%) and highest fill factor (FF) value (89.42%). The lowest excitation binding energy is estimated by newly designed molecule M2 (E b = 0.30 eV), which indicates a higher rate of dissociation during the excitation as observed in transition density matrix (TDM) plots. Utilizing electron density difference maps, the newly designed molecules in dichloromethane solvent exhibited consistent intramolecular charge transfer (ICT). The designed molecules were evaluated against reference molecule R to determine if they exhibit superior optoelectronic capabilities. It is found that all designed molecules (M1-M5) exhibit reduced band gaps, are red-shifted in wavelength in comparison to a reference molecule R, and have remarkable charge motilities in terms of reorganisation energies.

Versatile Solvatochromic fluorophores based on Schiff bases for colorimetric detection of metal ions

In recent years, fluorescent probes have been extensively studied as powerful tools for the effective assessment of toxic metal ions due to their high sensitivity, selectivity, capability for real-time and non-invasive monitoring, and versatility. In this paper, novel fluorescent probes based on Schiff bases, namely 2-((1E,2E)-1-(6-chlorobenzo[d]thiazol-2-ylimino)-3-(4-(dimethylamino)phenyl)allyl)phenol (1) and 2-((1E,2E)-3-(4-(dimethylamino)phenyl)-1-(4-methylbenzo[d]thiazol-2-ylimino)allyl)phenol (2), were synthesized and characterized. The optical properties of these probes were examined across a spectrum of fourteen solvents with varying polarities, revealing significant solvatochromic effects on both absorption and fluorescence spectra. The analysis delineated a discernible difference in dipole moment between electronic ground and excited states, with molecules exhibiting enhanced stabilization in singlet excited states. Subsequently, a straightforward method was devised for the selective and sensitive detection of diverse metal ions in aqueous solutions, including K+, V3+, Cr3+, Fe3+, Co2+, Ni2+, Cu2+, Se6+, Cd2+, Ba2+, and Hg2+, through naked eye observation, UV–Visible, and fluorimetric measurements. Notably, the UV–Vis spectra of probes 1 and 2 manifested a significant red shift upon the addition of metal ions, indicative of potential ligand-to-metal charge-transfer (LMCT) phenomena, with the exception of Ni2+, Cu2+, and Se6+ions. The observed alterations in optical absorption and fluorescence emission contributed to the probes' heightened selectivity and sensitivity, obviating the necessity for sample pretreatment. Competitive assays underscored the probes' preference for Cr3+ and V3+ ions over other common metal ions. Furthermore, Job's plot analysis suggested a 1:1 ligand-to-metal molar ratio binding. The investigated Schiff bases exhibited elevated binding constants (Ka), low detection limits, and limits of quantification, alongside diminished fluorescence quantum yield. Leveraging fluorescence quenching, facile paper-based sensor strips coated with Schiff bases facilitated prompt, qualitative, and quantitative in situ detection of metal ions in aqueous solutions across a broad concentration spectrum, discernible to the naked eye under UV light.

Enhanced N-type Semiconducting Performance of Asymmetric Monochlorinated Isoindigo-based Semiregioregular Polymers under Dynamic Forces.

The asymmetric monochlorination strategy not only effectively addresses the steric issues in conventional dichlorination but also enables the development of promising acceptor units and semiregioregular polymers. Herein, monochlorinated isoindigo (1CIID) is successfully designed and synthesized by selectively introducing single chlorine (Cl) atoms. Furthermore, the 1CIID copolymerizes with two donor counterparts, centrosymmetric 2,2'-bithiophene (2T) and axisymmetric 4,7-di(thiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT), forming two polymers, P1CIID-2T and P1CIID-DTBT. These polymers exhibit notable differences in backbone linearity and dipole moments, influenced by the symmetry of their donor counterparts. In particular, P1CIID-2T, which contains a centrosymmetric 2T unit, demonstrates a linear backbone and a significant dipole moment of 10.20 D. These properties contribute to the favorable film morphology of P1CIID-2T, characterized by highly ordered crystallinity in the presence of fifth-order (500) X-ray diffraction peaks. Notably, P1CIID-2T exhibits a significant improvement in molecular alignment under dynamic force, resulting in over 8-fold improvement in the performance of organic field-effect transistor (OFET) devices, with superior electron mobility up to 1.22 cm2 V-1 s-1. This study represents the first synthesis of asymmetric monochlorinated isoindigo-based conjugated polymers, highlighting the potential of asymmetric monochlorination for developing n-type semiconducting polymers. Moreover, our findings provide valuable insights into the relationship between the molecular structure and properties.

Solvent-polarity dependence of ultrafast excited-state dynamics of trans-4-nitrostilbene.

Ultrafast excited-state dynamics of the simplest nitrostilbenes, namely trans-4-nitrostilbene (t-NSB), was studied in solvents of various polarities with ultrafast broadband time-resolved fluorescence and transient absorption spectroscopies, and by quantum-chemical computations. The results revealed that the initially excited S1(ππ*) state deactivation dynamics is strongly influenced by the solvent polarity. Specifically, the t-NSB S1-state lifetime decreases by three orders of magnitude from ∼60 ps in high-polarity solvents to ∼60 fs in nonpolar solvents. The strong solvent-polarity dependence arises from the differences in dipole moments among the S1 and relevant states, including the major intersystem crossing (ISC) receiver triplet states, and therefore, the solvent polarity can modulate their relative energies and ISC rates. In nonpolar solvents, the sub-100 fs lifetime is due to a combination of efficient ISC and internal conversion. In medium-polarity solvents, the S1-state population decays via a competing ISC relaxation mechanism in a biphasic manner, and the ISC rates are found to obey the inverse energy gap law of the strong coupling case. In high-polarity solvents, the S1 state is stabilized to a much lower energy such that ISC becomes energetically infeasible, and the S1 state decays via barrier crossing along the torsion angle of the central ethylenic bond to the nonfluorescent perpendicular configuration. Regardless of the initial S1-state deactivation pathways in various solvents, the excited-state population is ultimately trapped in the metastable T1-state perpendicular configuration, at which a slower ISC occurs to bring the system to the ground state and bifurcate into either trans or cis form of NSB.

ADME profiling, molecular docking, DFT, and MEP analysis reveal cissamaline, cissamanine, and cissamdine from Cissampelos capensis L.f. as potential anti-Alzheimer's agents.

The current pharmacotherapies for Alzheimer's disease (AD) demonstrate limited efficacy and are associated with various side effects, highlighting the need for novel therapeutic agents. Natural products, particularly from medicinal plants, have emerged as a significant source of potential neuroprotective compounds. In this context, Cissampelos capensis L.f., renowned for its medicinal properties, has recently yielded three new proaporphine alkaloids; cissamaline, cissamanine, and cissamdine. Despite their promising bioactive profiles, the biological targets of these alkaloids in the context of AD have remained unexplored. This study undertakes a comprehensive in silico examination of the binding affinity and molecular interactions of these alkaloids with human protein targets implicated in AD. The drug likeness and ADME analyses indicate favorable pharmacokinetic profiles for these compounds, suggesting their potential efficacy in targeting the central nervous system. Molecular docking studies indicate that cissamaline, cissamanine, and cissamdine interact with key AD-associated proteins. These interactions are comparable to, or in some aspects slightly less potent than, those observed with established AD drugs, highlighting their potential as novel therapeutic agents for Alzheimer's disease. Crucially, Density Functional Theory (DFT) calculations offer deep insights into the electronic and energetic characteristics of these alkaloids. These calculations reveal distinct electronic properties, with differences in total energy, binding energy, HOMO-LUMO gaps, dipole moments, and electrophilicity indices. Such variations suggest unique reactivity profiles and molecular stability, pertinent to their pharmacological potential. Moreover, Molecular Electrostatic Potential (MEP) analyses provide visual representations of the electrostatic characteristics of these alkaloids. The analyses highlight areas prone to electrophilic and nucleophilic attacks, indicating their potential for specific biochemical interactions. This combination of DFT and MEP results elucidates the intricate electronic, energetic, and electrostatic properties of these compounds, underpinning their promise as AD therapeutic agents. The in silico findings of this study shed light on the promising potential of cissamaline, cissamanine, and cissamdine as agents for AD treatment. However, further in vitro and in vivo studies are necessary to validate these theoretical predictions and to understand the precise mechanisms through which these alkaloids may exert their therapeutic effects.

Tunable polarization properties of charge, spin, and valley in Janus VSiGeZ4 (Z = N, P, As) monolayers.

Polarization, as an important characterization of the symmetry breaking systems, has attracted tremendous attention in two-dimensional (2D) materials. Due to their significant symmetry breaking, Janus 2D ferrovalley materials provide a desirable platform to investigate the charge, spin, and valley polarization, as well as their coupling effects. Herein, using first-principles calculations, the polarization properties of charge, spin, and valley in Janus VSiGeZ4 (Z = N, P, and As) monolayers are systematically studied. The mirror symmetry breaking leads to a non-zero dipole moment and surface work function difference, indicating the presence of out-of-plane charge polarization. Magnetic properties calculations demonstrate that VSiGeN4 is a 2D-XY magnet with a Berezinskii-Kosterlitz-Thouless temperature of 342 K, while VSiGeP4 and VSiGeAs4 have an out-of-plane magnetization with a Curie temperature below room temperature. The magnetization can be rotated by applying biaxial strain, allowing manipulation of the spin polarization via nonmagnetic means. The spontaneous valley polarization is predicted to be 46, 49, and 70 meV for VSiGeN4, VSiGeP4, and VSiGeAs4, respectively, whose physical origin can be elucidated by employing the model analysis. In particular, the biaxial strain can induce the valley polarization switching from the valence (conduction) band to conduction (valence) band, but it hardly changes the valley polarization strength. Meanwhile, the valley extremum is transformed from the K' (K) to K (K') points. The present work not only provides an underlying insight into the polarization properties of Janus VSiGeZ4 but also offers a class of promising materials for spintronic and valleytronic devices.

Photophysical properties of 3-arylthioimidazo[1,2-a]pyridine derivatives: The role of peripheral electron-donating and electron-withdrawing groups in the advance of organic materials engineering

3-Arylthioimidazo[1,2-a]pyridine derivatives may present potential use in fields such as optoelectronics, organic light-emitting diodes (OLEDs), bioimaging, and may be employed as bioprobes in DNA and RNA. However, before these materials can be used for such applications, it is necessary to assess their photophysical properties. Here, we investigated the photophysical properties of five novel 3-arylthioimidazo[1,2-a]pyridine derivatives with different peripheral electron-withdrawing and electron-donating groups. The use of spectroscopic techniques, including UV–vis absorption, fluorescence, time-resolved fluorescence spectroscopy, combined with quantum chemical calculations, allowed us to gain a comprehensive understanding of the compounds' photophysical properties. The results revealed that the 3-arylthioimidazo[1,2-a]pyridine derivatives possess remarkable emissive properties, with a 4.5-fold increase when substituting the trifluoromethyl group for a methoxy group. Furthermore, it has been observed that the compounds containing peripheral groups with halogen atoms exhibit fluorescence quenching. The electron-withdrawing character of the imidazo[1,2-a]pyridine and the position of the lateral substituent hindered the impact of electron-withdrawing groups, while electron-donating groups enhanced the photophysical properties, resulting in increased Stokes shift, larger permanent dipole moment difference, and charge displacement. In conclusion, this study provides key insights into the photophysics of 3-arylthioimidazo[1,2-a]pyridine derivatives and the role of peripheral electron-donating and electron-withdrawing groups. These findings hold great potential for the advancement of optical materials and set foundation for future technological applications.

AP-x,y Equilibrium data of the binary systems of 1-Butanol and 2-Butanol with argon at 313.15 K and 333.15 K – Measurements and modeling

The equilibrium composition of two binary systems (argon–1-butanol and argon–2-butanol) was measured at 313.15 K and 333.15 K and at pressures up to 640 bar. A high-pressure optical view cell was used for the experiments, while theoretical calculations were based on the Peng-Robinson Equation of State with the Boston-Mathias alpha function. Different equilibrium compositions of argon in butanol isomers, as well as butanol isomer in argon were observed despite the similar molecular weight of isomers (M1-butanol = 74.121 g mol−1 and M2-butanol = 74.122 g mol−1) and a functional hydroxyl group. The difference in vapour pressure, dipole moment and solute-solute interactions lead to different solubility values. Nevertheless, the importance of data predicted by theoretical calculations is based on the possibility of obtaining an approximation to the thermodynamic behaviour of the real systems without the necessity of experimental data.

Influence of peripherical modifications in linear and nonlinear photophysical properties of imidazo[4,5-b]pyridine derivatives

This study reports a wide study on linear and nonlinear optical properties of six imidazo[4,5-b]pyridines derivates. The compounds are coupled with a series of peripheral groups forming different dipolar structures (D-π-A and A-π-A). Photophysical parameters such as the anisotropy coefficient, transition dipole moment, and permanent dipole moment difference were determined using spectroscopic techniques. The two-photon absorption (2PA) cross-section spectra were obtained by the tunable femtosecond Z-scan technique. In addition, quantum chemical calculations and the Sum Over States (SOS) model for two energy levels were applied to support the experimental data. A single 2PA band, with 2PA cross-section varying from 70 to 110 GM, was observed in the 2PA cross-section spectra in the molecules with only acceptor groups. In addition, the presence of a second band around 660 nm and an increase in 2PA cross-section values (around 110 to 130 GM in the principal band) was observed for the molecules with a combination of the methoxy radical (OMe) with halogen groups (D-π-A structure). These results indicate that the non-centrosymetric A-Imp-D structures facilitate the polarizability and internal charge transfer processes, resulting in photophysical and two-photon absorption properties enhancement compared to A-Imp-A structures.

Temperature-Tuned Variable Confined Space for Modulating Dipolar Polarization of a Disc-Shaped Ammonium Ion.

Free accessible confined space and loose interaction are crucial for most solid-state ionic motions. Here, by using a near-spherical anion and a disc-shaped ammonium as two distinct but rigid building blocks, we report a new ionic crystal, (HMIm)3[La(NO3)6] (HMIm = 1-methyl-1H-imidazol-3-ium), in which the different confined spaces of three (HMIm)+ ions are fine-tuned over a broad temperature range. This effect can be utilized to modulate the dipolar polarization across a wide temperature/frequency range. Additionally, small-scale substitution of (HMIm)+ by its isomer of almost identical shape/size affords molecular solid solutions, which can further tune the dipolar polarization by varying the doping ratio. It is revealed that the differences in dipole moment and hydrogen bond rather than that of shape/size lead to a distorted crystalline environment for these solid solutions. Overall, we provide an exceptional model for understanding and regulating the dipole motion of polar aromatic molecules/ions in a crystalline environment.

Predict the Polarizability and Order of Magnitude of Second Hyperpolarizability of Molecules by Machine Learning.

In order to determine the polarizability and hyperpolarizability of a molecule, several key parameters need to be known, including the excitation energy of the ground and excited states, the transition dipole moment, and the difference of dipole moment between the ground and excited states. In this study, a machine-learning model was developed and trained to predict the molecular polarizability and second-order hyperpolarizability on a subset of QM9 data set. The density of states was employed as input to the model. The results demonstrated that the machine-learning model effectively estimated both polarizability and the order of magnitude of second-order hyperpolarizability. However, the model was unable to predict the dipole moment and first-order hyperpolarizability, suggesting limitations in its ability to predict the difference of dipole moment between the ground and excited states. The computational efficiency of machine-learning models compared to traditional quantum mechanical calculations enables the possibility of large-scale screening of molecules that satisfy specific requirements using existing databases. This work presents a potential solution for the efficient exploration and analysis of molecules on a larger scale.

Resolving the Emission Transition Dipole Moments of Single Doubly Excited Seeded Nanorods via Heralded Defocused Imaging.

Semiconductor nanocrystal emission polarization is a crucial probe of nanocrystal physics and an essential factor for nanocrystal-based technologies. While the transition dipole moment for the lowest excited state to ground state transition is well characterized, the dipole moment of higher multiexcitonic transitions is inaccessible via most spectroscopy techniques. Here, we realize direct characterization of the doubly excited-state relaxation transition dipole by heralded defocused imaging. Defocused imaging maps the dipole emission pattern onto a fast single-photon avalanche diode detector array, allowing the postselection of photon pairs emitted from the biexciton-exciton emission cascade and resolving the differences in transition dipole moments. Type-I1/2 seeded nanorods exhibit higher anisotropy of the biexciton-to-exciton transition compared to the exciton-to-ground state transition. In contrast, type-II seeded nanorods display a reduction of biexciton emission anisotropy. These findings are rationalized in terms of an interplay between the transient dynamics of the refractive index and the excitonic fine structure.

1,7-, 1,6-, and 1,6,7- Derivatives of dodecylthio perylene diimides: Synthesis, characterization, and comparison of electrochemical and optical properties

The synthesis, separation, and characterization of 1,6-, 1,7-, and 1,6,7- derivatives of dodecylthio–N,N’– (2,4–diisopropylphenyl)-3,4,9,10-perylenetetracarboxylic diimide are reported. The three derivatives display noticeable differences in their electronic absorption and emission properties, with a bathochromic shift in spectral maxima from 1,6–Thio–PDI, to 1,7–Thio–PDI, to 1,6,7–Thio–PDI. The 1,7–Thio–PDI derivative had the highest fluorescence quantum yield and longest fluorescence lifetime in toluene (ΦF = 0.85, τF = 8.3 ns), followed by 1,6–Thio–PDI (ΦF = 0.54, τF = 6.6 ns) and 1,6,7–Thio–PDI (ΦF = 0.16, τF = 4.4 ns). The difference in dipole moment between the ground and excited states were estimated by the Lippert-Mataga analysis of solvent dependent absorption and emission properties and ranged from Δμ = 7.1 Debye for 1,6,7–Thio–PDI to 8.3 Debye for 1,6–Thio–PDI. These measurements were supported by time–dependent density functional theory calculations, which helped interpret the differences in absorption spectra. Cyclic voltammetry showed minor differences in the reduction potentials for the singly and doubly reduced states. The absorption spectra of the singly and doubly reduced states are also reported.

Engineering of Pyroelectric Crystals Decoupled from Piezoelectricity as Illustrated by Doped α‐Glycine

AbstractDesign of pyroelectric crystals decoupled from piezoelectricity is not only a topic of scientific curiosity but also demonstrates effects in principle that have the potential to be technologically advantageous. Here we report a new method for the design of such materials. Thus, the co‐doping of centrosymmetric crystals with tailor‐made guest molecules, as illustrated by the doping of α‐glycine with different amino acids (Threonine, Alanine and Serine). The polarization of those crystals displays two distinct contributions, one arising from the difference in dipole moments between guest and host and the other from the displacement of host molecules from their symmetry‐related positions. These contributions exhibit different temperature dependences and response to mechanical deformation. Thus, providing a proof of concept for the ability to design pyroelectric materials with reduced piezoelectric coefficient (d22) to a minimal value, below the resolution limit of the method (<0.005 pm/V).

Engineering of Pyroelectric Crystals Decoupled from Piezoelectricity as Illustrated by Doped α-Glycine.

Design of pyroelectric crystals decoupled from piezoelectricity is not only a topic of scientific curiosity but also demonstrates effects in principle that have the potential to be technologically advantageous. Here we report a new method for the design of such materials. Thus, the co-doping of centrosymmetric crystals with tailor-made guest molecules, as illustrated by the doping of α-glycine with different amino acids (Threonine, Alanine and Serine). The polarization of those crystals displays two distinct contributions, one arising from the difference in dipole moments between guest and host and the other from the displacement of host molecules from their symmetry-related positions. These contributions exhibit different temperature dependences and response to mechanical deformation. Thus, providing a proof of concept for the ability to design pyroelectric materials with reduced piezoelectric coefficient (d22 ) to a minimal value, below the resolution limit of the method (<0.005 pm/V).

Synthesis and Nonlinear Optical Behavior of Thermally Stable Chromophores Based on 9,9-Dimethyl-9H-fluoren-2-amine: Improving Intrinsic Hyperpolarizability through Modulation of "Push-Pull".

Improvement in the first hyperpolarizability (βHRS) as well as intrinsic hyperpolarizability (βint) of chromophores based on 9,9-dimethyl-9H-fluoren-2-amine through modulation of the conjugation pathway is described. A series of six novel chromophores with "linear" conjugation showed significant enhancement of βHRS as well as βint compared to the counterparts lacking a "linear" conjugation but having an identical combination of donor, acceptor, and the intervening π-conjugated linker. The hyperpolarizability (βHRS as well as βint) values of the new series measured using hyper-Rayleigh scattering exceeded the apparent limit set by the latter set of fluorene-based chromophores. The experimental results are analyzed and interpreted in the context of linear optical properties, single-crystal X-ray analysis, electrochemistry, etc. and corroborated by theoretical studies. We find that modulation of the "push-pull" of the conjugation pathway in these donor-acceptor chromophores compares favourably with the corresponding changes in the optical gaps, transition dipole moments, and dipole moment difference between the ground and excited states.

Development of biphasic solvent for CO2 capture by tailoring the polarity of amine solution

A facile screening method for amine/phase splitter/H2O biphasic solvents was proposed. The polarity difference between the high polarity absorption products and the low polarity phase splitter was recognized as the decisive factor for phase separation. In this study, biphasic solvent was developed by tailoring the polarity of absorption products. It’s revealed that the amine/1-propanol/H2O solvents with a dipole moment difference above 6.0 Debye featured phase separation. After screening, TETA/1-propanol/H2O biphasic absorbent with high CO2-rich loading and low regeneration energy was developed. The phase separation behavior was affected by TETA concentration, 1-propanol concentration, and the absorption temperature. Remarkably, the CO2 capacity and volume distribution of the rich phase can be simply tuned by altering the 1-propanol concentration. For the optimal composition of 30 wt% TETA and 50 wt% 1-propanol, a rapid phase separation in 2 min was observed at 60 °C. And the rich phase exhibited a CO2 capacity as high as 6.06 mol/L with a volume proportion of 38.9%. With the promotion of 1-propanol, the CO2 mass transfer coefficient in TETA/1-propanol reached 21.4 × 10−11 mol/cm2·s·Pa, 42.7% higher than 30 wt% TETA and 110.2% higher than 30 wt% MEA. The estimated regeneration heat was 2.06 GJ/t CO2, 48.4% lower than 30 wt% MEA. This research provided a facile screening method and a promising alternative absorbent for CO2 capture.

Effect of peripherical groups on the two-photon brightness of (E)-3-benzyl-6-bromo-2-styryl-3H-imidazo[4,5-b]pyridine derivatives

Here, a study of the effect of several electron-withdrawing (F, Br, CF3, Cl) and electron-donating (OMe, OTBDMS, CH3, S) on the two-photon brightness (2 PB) of nine imidazo[4,5-b]pyridine derivatives was developed. The two-photon absorption cross-section (2PACS) spectra were acquired by the tunable femtosecond Z-scan technique from 470 nm up to 700 nm, and hence the 2 PB was evaluated at the 2PACS peak (around 540 nm) and 700 nm. Transition dipole moment, the difference of state dipole moments, anisotropy coefficient, and fluorescence lifetime were figured out as a result of the Gaussian decomposition of one-photon absorption spectra, solvatochromism, fluorescence anisotropy, and Strickler Berg equation, respectively. Besides the photophysical analysis, the photophysical parameters were used as input parameters to phenomenologically model the 2PACS applying the Sum-Over-States approach regarding a three-level energy system. Results have shown a 2PACS peak of around 130 GM for all imidazo[4,5-b]pyridine derivatives, and values of 2PACS at 700 nm ranged from 4 up to 14 GM. Results show that for Br-π-electron withdrawing (Br-π-EW) molecular arrangement, higher values of 2 PB can be reached, mainly through the control of ϕ, which demonstrated to be more sensible than the 2PACS to the addition of different peripherical groups.

Solvatochromic study of triphenylamine derivatives: Estimation of the permanent dipole moment difference

Solvatochromic study of triphenylamine derivatives: Estimation of the permanent dipole moment difference