Dipole Moment Difference Research Articles

Computational design of ratiometric two-photon fluorescent Zn2+ probes based on quinoline and di-2-picolylamine moieties

To improve two-photon absorption (TPA) response of a newly synthesized probe, a series of ratiometric two-photon fluorescent Zn2+ sensors based on quinoline and DPA moieties have been designed. The one-photon absorption, TPA, and emission properties of the experimental and designed probes before and after coordination with Zn2+ are investigated employing the density functional theory in combination with response functions. The design consists of two levels. In the first level of design, five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores. It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer. Moreover, it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone. One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups. Therefore, in the second level of design, a new probe 7 is formed by both an acyl unit and a dimethylamino terminal. It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically. Furthermore, the fluorescence quantum yields of the designed probes 4 and 7 are calculated in a new way, which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield. The result shows that our design also improves the fluorescence quantum yield considerably. All in all, the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn2+ coordination and strong fluorescence intensity, which demonstrates that they are potential ratiometric two-photon fluorescent probes.

Influence of electron-withdrawing groups in two-photon absorption of imidazopyridines derivatives

This work investigates the influence of different electron-withdrawing groups (Cl, Br, fluorobenzonitrile), on the two-photon absorption cross-section of six imidazo[4,5-b]pyridine derivatives. The two-photon absorption cross-section spectra were obtained by ultra-fast Z-scan technique from 470 nm up to 700 nm. The Sum-Over-States approach was applied to model the two-photon absorption spectra, using a three-level energy system. Photophysical properties, such as transition dipole moment, the difference of permanent dipole moments, and anisotropy coefficient were determined through the analysis of one-photon absorption spectra, solvatochromism, and fluorescence anisotropy, respectively. Besides, the excited state absorption spectra were measured through ultra-fast transient absorption, allowing the excited state lifetime and spectral position determination. Two-photon absorption cross-sections of about 160 GM were observed when two electron-withdrawing groups are linked to the imidazo[4,5-b]pyridine core, elucidating a path to achieve high optical nonlinearities in imidazopyridine derivatives. Furthermore, a increase in the two-photon cross-section was observed when chloride is linked at the C-6 position (90 GM) instead of the C-5 position (50 GM), which is related to the proximity of a higher excited state.

Density Functional Theory Study of Substitution Effects on the Second-Order Nonlinear Optical Properties of Lindquist-Type Organo-Imido Polyoxometalates

Density functional theory and time-dependent density functional theory have been enacted to investigate the effects of donor and acceptor on the first hyperpolarizability of Lindquist-type organo-imido polyoxometalates (POMs). These calculations employ a range-separated hybrid exchange-correlation functional (ωB97X-D), account for solvent effects using the implicit polarizable continuum model, and analyze the first hyperpolarizabilities by using the two-state approximation. They highlight the beneficial role of strong donors as well as of π-conjugated spacers (CH=CH rather than C≡C) on the first hyperpolarizabilities. Analysis based on the unit sphere representation confirms the one-dimensional push-pull π-conjugated character of the POMs substituted by donor groups and the corresponding value of the depolarization ratios close to 5. Furthermore, the use of the two-state approximation is demonstrated to be suitable for explaining the origin of the variations of the first hyperpolarizabilities as a function of the characteristics of a unique low-energy charge-transfer excited state and to attribute most of the first hyperpolarizability changes to the difference of dipole moment between the ground and that charge-transfer excited state.

Electrostatic charge controls the lowest LH1 Qy transition energy in the triply extremophilic purple phototrophic bacterium, Halorhodospira halochloris

Halorhodospira (Hlr.) halochloris is a unique phototrophic purple bacterium because it is a triple extremophile—the organism is thermophilic, alkalophilic, and halophilic. The most striking photosynthetic feature of Hlr. halochloris is that the bacteriochlorophyll (BChl) b-containing core light-harvesting (LH1) complex surrounding its reaction center (RC) exhibits its LH1 Qy absorption maximum at 1016 nm, which is the lowest transition energy among phototrophic organisms. Here we report that this extraordinarily red-shifted LH1 Qy band of Hlr. halochloris exhibits interconvertible spectral shifts depending on the electrostatic charge distribution around the BChl b molecules. The 1016 nm band of the Hlr. halochloris LH1-RC complex was blue-shifted to 958 nm upon desalting or pH decrease but returned to its original position when supplemented with salts or pH increase. Resonance Raman analysis demonstrated that these interconvertible spectral shifts are not associated with the strength of hydrogen-bonding interactions between BChl b and LH1 polypeptides. Furthermore, circular dichroism signals for the LH1 Qy transition of Hlr. halochloris appeared with a positive sign (as in BChl b-containing Blastochloris species) and opposite those of BChl a-containing purple bacteria, possibly due to a combined effect of slight differences in the transition dipole moments between BChl a and BChl b and in the interactions between adjacent BChls in their assembled state. Based on these findings and LH1 amino acid sequences, it is proposed that Hlr. halochloris evolved its unique and tunable light-harvesting system with electrostatic charges in order to carry out photosynthesis and thrive in its punishing hypersaline and alkaline habitat.

A combined quantum chemical, molcular dynamics and Monto Carlo study of three amino acids as corroison inhibitors for aluminum in NaCl solution

The performance of arginine (Arg), glutamine (Glu), and asparagine (Asp) in inhibiting the corrosion of aluminum in NaCl solution and the inhibition mechanism at atomic level are investigated via the combination of the quantum chemistry (QM) calculations, molecular dynamics (MD) and Monte Carlo (MC) simulations to reveal the relationship among chemical structure, composition and performance. QM results show that differences in EHOMO, ELUMO, ΔEgap, dipole moment, global softness and hardness, and ESP charge lead to differences in inhibition efficiency. MC results show that the adsorption energy in aqueous environment for Arg, Glu, and Asp is −210.39, −69.22, and −66.88 Kcal mol−1, respectively. Results showed that inhibition efficiency is high when the absolute value of adsorption energy is high. MD simulation show that the peak distance of relative concentration function of Cl- is 17.45, 18.96, and 20.06 Å for Arg, Glu and Asp, respectively. The diffusion coefficient of Cl- in inhibitor film for Arg, Glu, Asp is 5.18 × 10−8, 8.01 × 10−8, 1.22 × 10−7 cm2 s−1, respectively. Both the adsorption energy and the ability to inhibit the diffusion and aggregation of corrosion particles determine the corrosion inhibition performance. The theoretical calculated inhibition ability is Arg＞Glu＞Asp, in good agreement with the experiment results. This paper provides a theoretical reference for further research on amino acid corrosion inhibitors.

Substituent Effects on the Solubility and Electronic Properties of the Cyanine Dye Cy5: Density Functional and Time-Dependent Density Functional Theory Calculations.

The aggregation ability and exciton dynamics of dyes are largely affected by properties of the dye monomers. To facilitate aggregation and improve excitonic function, dyes can be engineered with substituents to exhibit optimal key properties, such as hydrophobicity, static dipole moment differences, and transition dipole moments. To determine how electron donating (D) and electron withdrawing (W) substituents impact the solvation, static dipole moments, and transition dipole moments of the pentamethine indocyanine dye Cy5, density functional theory (DFT) and time-dependent (TD-) DFT calculations were performed. The inclusion of substituents had large effects on the solvation energy of Cy5, with pairs of withdrawing substituents (W-W pairs) exhibiting the most negative solvation energies, suggesting dyes with W-W pairs are more soluble than others. With respect to pristine Cy5, the transition dipole moment was relatively unaffected upon substitution while numerous W-W pairs and pairs of donating and withdrawing substituents (D-W pairs) enhanced the static dipole difference. The increase in static dipole difference was correlated with an increase in the magnitude of the sum of the Hammett constants of the substituents on the dye. The results of this study provide insight into how specific substituents affect Cy5 monomers and which pairs can be used to engineer dyes with desired properties.

Effect of Polymerization on the Charge-Transfer Mechanism in the One (Two)-Photon Absorption Process of D-A-Type Triphenylamine Derivatives.

To investigate the effect of polymerization (n = 1, 2, 3, and 4) on the charge-transfer (CT) mechanisms in the one (two)-photon absorption (OPA and TPA) process of D-A-type triphenylamine derivatives, charge density difference is used to graphically represent the CT characteristics. A transition density matrix is utilized to reveal the direction of CT on different groups quantitatively. With the n increasing, electrons are mainly transferred between the groups in the middle position of the molecular chain during OPA and TPA processes. Simulated results show that the energy gap and excitation energy have a good linear relationship with the reciprocal of the polymerization degree. Importantly, the polymerization effect can effectively increase the electronic transmission capability, TPA performance, and second hyperpolarizability. Besides, the simplified sum over state model reveals the variation factor of the TPA cross-section and the second static hyperpolarizability. The McRae formula and Bakhshiev formula are used to estimate the difference of dipole moments, which is an important parameter of the second hyperpolarizability. The comprehensive analysis of the nonlinear optical (NLO) parameters of triphenylamine derivatives can provide some significant guidance for molecular design and improve the NLO performance of D-A molecular materials. Also, the thermodynamic parameters can provide some theoretical supports for solving practical problems.

Biochemical, Phytochemical and Antioxidant Analysis of Leaves and Seed of Fenugreek Plant

In the present study leaves and seeds of two different varieties of Fenugreek plant viz. Trigonella foenum gracium and Trigonella corniculata, collected from Bahawalpur, Pakistan were subjected to the biochemical, phytochemical and antioxidant analysis. The content of total sugars, non reducing sugars and reducing sugars in selected parts of these varities were found to be 5.007±0.101 to 8.133±0.223, 4.255±0.150 to 7.099±0.316 and 0.751±0.064 to 1.410±0.071 g/100g of dry weight respectively. Water soluble, salt soluble and total salt soluble protein content range from 1.172±0.001 to 6.015±0.132, 1.517±0.038 to 1.174±0.006 and 0.013±0.001 to 0.018±0.001 g/100 g of dry weight respectively and the total free amino acids ranged from 1.198±0.014 to 4.554±0.006 g/100 g of dry weight. The range of tannins and saponin contents in analyzed parts of these varities was found to be 0.057±0.009 to 0.117±0.025 and 0.083±0.012 to 0.0151±0.045 g /100g of dry weight respectively. Similarly, flavonoids and hydrogen cyanide content ranged from 0.021±0.000 to 0.055±0.004 and 0.0234±0.008 to 0.307±0.009 g/100g of dry weight respectively; while ascorbic acid content was found to be in the range of 0.068±0.08 to 0.267±0.031 g/100g of dry weight. Total phenolic acid content of the selected parts of these varities were estimated on the basis of difference in dipole moment and its range was observed from 0.0539±0.024 to 0.856±0.064 g/100g of dry weight. The total antioxidants analysis showed that ascorbic acid and trolox contents (mg Eqv./100g of extract) were found to be lower in Trigonella corniculata seeds (0.066±0.001 and 0.047±0.001 mg Eqv./100g respectively) and higher in Trigonella corniculata leaves (0.069±0.001 and 0.050±0.001 mg Eqv./100g respectively).The DPPH radical scavenging activity and reducing power were found to be in the range of 31.736±2.430 to 39.590±2.432 and 0.974±0.231 to 2.301±0.068 respectively. The different parts of studied varities of fenugreek plant, having higher values of %DPPH inhibition and reducing power showed least count of IC50 and vice versa.

Synthesis and photophysical properties of ditrifluoroacetoxyboron complexes with curcumin analogues

A new class of ditrifluoroacetoxyboron complexes were designed and synthesized by chelation reaction of curcumins with boron trifluoroacetate. Their photophysical behaviors were studied in different solvents, powder state and PMMA polymer films. The results indicated that these complexes revealed a green to yellow emission at 486–595 nm in solution or PMMA films and an orange to red emission at 598–710 nm in powder state. Especially, complex 2c displayed the strongest emission intensity, the highest quantum yield in solution and the longest fluorescence lifetime in powder state in these complexes. In addtion, the emission bathochromic shifts of these complexes as a function of the solvent polarity parameter ET(30) were investigated by Lippert–Mataga approximation. It was observed that these complexes exhibited the higher values of the dipole moment difference (Δμ) between the ground and excited states, which implied an intense intramolecular charge transfer characteristics and a noticeable emission solvatochromic effect.

Enhancement of one- and two-photon absorption and visualization of intramolecular charge transfer of pyrenyl-contained derivatives.

To further improve the pyrenyl-contained derivatives two-photon absorption (TPA) and third-order nonlinear optical (NLO) properties, three steps of optimization are employed based on experimental molecule PCVS-B: heteroatomic substitution, exchanging the position of double bonds and adding a branch. The contributions of π electrons to localized orbital locators and Mayer bond orders (LOL-π and IABπ) show that the second step can enhance the chemical interaction between pyrenyl and the branched-chain. Two visual methods of charge density difference (CDD) and transition density matrix (TDM) are combined to intuitively analyze the intramolecular charge transfer (ICT) process of one (two) photon absorption; results show that both following two steps can increase the degree of ICT on the conjugated plane of the pyrenyl. The sum over state (SOS) model was used to find out the dominant two-photon transition process. The difference between the dipole moments obtained by the McRae equation is applied to the three-state model, revealing the inherent law of the second static hyperpolarizability.

Solvatochromism and excited-state characteristics of fluorenone-1-carboxylic acid

The solvatochromism of the fluorenone derivative 9-fluorenone-1-carboxylic acid (9F1C) was examined in binary cyclohexane-tetrahydrofuran mixtures, along with a theoretical investigation of possible excited state decay pathways. This fluorenone derivative differs from many previously investigated derivatives in that it possesses an electron withdrawing substituent and possibly undergoes intramolecular hydrogen bonding and proton transfer. A conventional Lippert-Mataga analysis was applied to the measured steady-state absorption and emission spectra to estimate the dipole moment difference between ground and emitting excited states. The estimated difference of ~2.8 D was found to be slightly larger than the average value of previously estimated differences for unsubstituted fluorenone (~2.4 D). The 9F1C derivative also differed from unsubstituted fluorenone in that fluorescence emission decreased, rather than increased, with increasing solvent polarity. Interpreting the possible cause of this difference prompted time-dependent density functional theory (TD-DFT) calculations of the relative energies of non-hydrogen bonded and intra-molecular hydrogen bonded excited states. These calculations suggested that an explanation for the decrease in emission for non-hydrogen bonded species could be enhancement of an intersystem-crossing (ISC) pathway. However, these same calculations suggested this explanation could not account for possible decreased emission from intra-molecular hydrogen-bonded species.

Synthesis of novel viscosity sensitive pyrrolo-quinaldine based styryl dyes: Photophysical properties, electrochemical and DFT study

We have synthesized two novel styryl dyes namely (E)-2-(2-(9-butyl-9H-carbazol-3-yl)vinyl)-3,3,8-trimethyl-3H-pyrrolo[3,2-h]quinoline (PQC) and (E)-10-butyl-3-(2-(3,3,8-trimethyl-3H-pyrrolo[3,2-h]quinolin-2-yl)vinyl)-10H-phenothiazine (PQPT). These dyes were characterized by FT-IR, HR-MS, 1H and 13C NMR spectroscopy techniques. Both dyes displayed absorption wavelength within the range of 399−427 nm. Ranging from non-polar solvents towards polar solvents, these dyes exhibited emission wavelength and Stokes shift from 487−605 nm and 85−180 nm respectively. The photophysical study of these dyes in seven solvents suggested that these dyes show positive emission solvatochromism which was investigated from Reichardt's ET (30) plot, Lippert-Mattaga graph and MacRae solvent polarity scale plots. In addition, these dyes show evidence of intramolecular charge transfer properties which were explained with the assist of Wellers, Rettig plots and ground-excited states dipole moment difference. The electrochemical properties of these dyes were investigated with the help of cyclic voltammetry and differential pulse voltammetry. Viscosity sensitivity studies were also performed on the synthesised dyes in the methanol and polyethylene glycol 400 system with varying viscosity of the solvent system. The thermal properties of these dyes were investigated using TGA and DSC analysis, which shows that dyes were thermally stable up to 200 °C. The theoretical photophysical properties of these dye molecules was explored by density functional theory (DFT) along with the time dependent density functional theory (TD-DFT).

Effect of fluorination on exciton binding energy and electronic coupling in small molecule acceptors for organic solar cells

A detail study was performed to get deeper understanding of fluorination impact on intermolecular coupling and intermolecular interactions. Results showed that fluorine substitution plays an important role to modify the charge distribution or electrostatic potential as well non-covalent interaction between molecules. Dipole moment difference between ground and first excited states has increased while exciton binding energy has decreased by increasing the fluorine atoms. SM3 with asymmetric fluorine substitution showed higher transfer integral due to stronger attractive interactions. By proper substitution of fluorine atom, π-π stacking distance can be reduced to achieve higher electronic coupling. Substitution of fluorine atoms has increased the reorganization energy and non-linear optical response.

High first‐hyperpolarizabilities of thiobarbituric acid derivative‐based donor‐π‐acceptor nonlinear optical‐phores: Multiple theoretical investigations of substituents and conjugated bridges effect

AbstractA number of compounds including thiobarbituric acid derivative‐based acceptor unit and diverse donor moieties along with two types of π‐conjugated bridges have been constructed to aid in the design of the superior nonlinear optical (NLO) materials. The effect of varying the donor and bridge parts of this donor‐bridge‐acceptor system was analyzed in terms of structural and opto‐electronic parameters such as bond length alternation and ultraviolet‐visible absorption spectra. Various functionals with aug‐cc‐pVDZ basis set including B3LYP, PBE0, PBE38, BMK, CAM‐B3LYP, and ωB97XD were employed to calculate the static and dynamic first‐hyperpolarizabilities, and also the linear polarizabilities. Furthermore, the variation of the static first‐hyperpolarizabilities has been explained satisfactorily in the light of the sum‐over‐states method and two‐level model. The comprehensive study indicates that the coplanar compound D‐5 with the low electronic absorption energy, strongest oscillator strength paired with the largest ground, and excited state dipole moment difference generates a dramatical increase in its static and dynamic first‐hyperpolarizabilities, which would be the most worthwhile target for development as the NLO‐phores.

N-(O-methoxyphenyl)aza-15-crown-5-ether derivatives: Highly efficient and wide range nonlinear optical response based cation recognition

In this work, we demonstrate the recognition of cations by complexation of N-(O-methoxyphenyl)aza-15-crown-5-ether derivative (TZC) with alkali (Li+, Na+, K+), alkaline earth (Mg2+, Ca2+) and transition metal cations (Ni2+, Zn2+). The doping of mono- and divalent metal cations are used to significantly enhance the first hyperpolarizability values as compared to TZC. By utilizing density functional (DFT) methods, the parent molecule and metal-doped complexes have been optimized using B3LYP-D3/6-31G* level of theory. The amplitudes of first hyperpolarizability βtot have been obtained CAM-B3LYP and M06-2X functional for all studied systems. Interestingly, the atomic number, size, and charge of the metal cations and the O- and N-atoms of the crown-ether are found to be the major factor that gives rise to higher NLO response properties. From the natural bond orbital (NBO), localized orbital locator (LOL) and interactional energy analyses, alkali metal cations possessing a higher degree of ionic characteristics, whereas, the alkaline earth and transition metal cations possessing significant covalent characters. Furthermore, the frontier molecular orbital analysis and the TD-DFT studies reveal that the transition energies as a function of metal size and charge are responsible for remarkably enhanced and distinctive βtot amplitudes as large as TZC-Li+ 10,158 a.u., TZC-Mg2+ 21,948 a.u. and TZC-Ni2+ 25,483 a.u. Additionally, the electrostatic potential maps (ESP) and the difference of dipole moments (Δμ) from the ground to the first excited state have also been carried out to understand the abilities of these systems as highly efficient and selective metal cation sensors.

Theoretical study of a memory-based optical converter with degenerate Zeeman states

Coherent optical memory based on electromagnetically induced transparency (EIT) offers a convenient way to convert the frequency or polarization of an optical probe pulse by storing in one $\mathrm{\ensuremath{\Lambda}}$ system and retrieving in another $\mathrm{\ensuremath{\Lambda}}$ system. We present a theoretical study on the efficiency variation of such an EIT-memory-based optical converter in an atomic system with degenerate Zeeman states. Based on the Maxwell-Bloch equation, we obtain an approximate analytic solution for the converted light pulses which clarifies that two major factors affect the efficiency of the converted pulses. The first one is the finite bandwidth effect of the pulses and the difference in the delay-bandwidth product of the writing and reading channel due to the difference in the transition dipole moment. The second one is the mismatch between the stored ground-state coherence and the ratio of the Clebsch-Gordan coefficients for the probe and control transition in the reading channel, which results in a nonadiabatic energy loss. To correspond to real experimental conditions, we also perform a numerical calculation of the variation in conversion efficiency versus the Zeeman population distribution under the Zeeman-state optical pumping in storing a ${\ensuremath{\sigma}}^{+}$-polarized pulse and retrieving with ${\ensuremath{\sigma}}^{\ensuremath{-}}$ polarization in cesium atoms. Our work provides essential physical insights and quantitative knowledge for the development of a coherent optical converter based on EIT-memory.

Electric-Field-Induced Connectivity Switching in Single-Molecule Junctions.

SummaryThe manipulation of molecule-electrode interaction is essential for the fabrication of molecular devices and determines the connectivity from electrodes to molecular components. Although the connectivity of molecular devices could be controlled by molecular design to place anchor groups in different positions of molecule backbones, the reversible switching of such connectivities remains challenging. Here, we develop an electric-field-induced strategy to switch the connectivity of single-molecule junctions reversibly, leading to the manipulation of different connectivities in the same molecular backbone. Our results offer a new concept of single-molecule manipulation and provide a feasible strategy to regulate molecule-electrode interaction.

Systematic Control of Structural and Photophysical Properties of π-Extended Mono- and Bis-BODIPY Derivatives.

A series of π-extended mono- and bis-BODIPY (BODIPY=boron-dipyrromethene) derivatives, namely, benzo[a]phenanthrene-fused BODIPY (Phena-Mono-BDP), benzo[a]anthracene-fused BODIPY (Ant-Mono-BDP), and dibenz[a,h]anthracene (DBA)-bridged bis-BODIPY (Ant-Bis-BDP), were designed and synthesized to examine their structural, electrochemical, and photophysical properties. Single-crystal X-ray crystallographic analyses demonstrated the planar configuration of Ant-Mono-BDP, in contrast to that of nonplanar Phena-Mono-BDP, whereas Ant-Bis-BDP has a DBA-centered planar configuration and two terminal nonplanar units of BODIPYs. The oxidation and reduction potentials agree with the estimated energies obtained through DFT calculations. The localized HOMO and LUMO states suggested the intramolecular charge-transfer characteristics in these BODIPY derivatives. The absorption spectra of these compounds extended up to the near-IR region. Strong redshifted trends of fluorescence spectra were observed in Ant-Bis-BDP with increasing solvent polarity, as supported by the differences in dipole moments estimated from Lippert-Mataga plots. To evaluate the excited-state dynamics of these molecules, the fluorescence quantum yield (ΦFL ) of Ant-Bis-BDP dramatically increased in the range from 0.05 to 0.86, with decreasing solvent polarity. Finally, the efficient two-photon absorption cross section of Ant-Bis-BDP (ca. 1200 GM at λ=1000 nm) was also obtained by considering the large π-extended structure (acceptor-donor-acceptor type).

Efficient and hysteresis-less perovskite and organic solar cells by employing donor-acceptor type π-conjugated polymer

Abstract The development of new and efficient donor-acceptor (D-A)-type π-conjugated polymers has attracted significant attention in the field of organic electronics owing to their fascinating features. Herein, we explore a new and efficient D-A-type π-conjugated polymer, poly[4,8-bis(2-(4-(2-ethylhexyloxy)phenyl)-5-thienyl)benzo[1,2-b:4,5-b′]dithiophene-alt-1,3-bis(6-octylthieno [3,2-b]thiophen-2-yl)-5-(2-hexyldecyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione] (P-TT-TPD) for perovskite solar cells (PSCs) and organic solar cells (OSCs). The well suited energy levels, high mobility, solution processability, high dipole moment difference between the ground and excited states and better passivation of P-TT-TPD delivered a high power conversion efficiency (PCE) of 17.10% and 17.56% in dopant-free and tris(pentafluorophenyl)borane-doped PSCs, respectively, with negligible hysteresis factor. To the best of our knowledge, this is the only polymer hole transporting material (HTM) showing negligible hysteresis factor values in both pristine and doped states. Moreover, P-TT-TPD was also used as a photoactive donor material in fullerene-based OSCs and it displayed a decent PCE of 6.19%. These study results demonstrate that the molecular engineering of a D-A-type π-conjugated polymer is an effective strategy to design multi-functional π-conjugated materials capable of working as both an HTM and a photoactive donor material.

Synthesis, photophysical and solvatochromic properties of diacetoxyboron complexes with curcumin derivatives.

Five novel diacetoxyboron complexes of β-diketones incorporated curcumin moiety were designed and synthesized. Their photophysical behaviors were investigated by UV-vis absorption and fluorescence spectroscopy in different solvents and solid state. It was observed that their fluorescence spectra yielded a blue to yellow-green emission in solution and emitted a yellow to red emission in solid state. Especially, the complex 3b displayed the strongest emission and the highest quantum efficiency (Φu = 0.98) in toluene among these complexes. The CIE coordinate of the complex 3b in solid state was positioned in an ideal red region of the chromaticity diagram. The maximal emission of these complexes exhibited a large wavelength shift and Stokes shift increased with the increase of the solvent polarity. Their dipole moment differences between the ground and excited states were also estimated by using the Lippert-Mataga equation. Meanwhile, their HOMO, LUMO energy levels and energy band gaps were calculated by cyclic voltammetry.