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Herein, we have synthesized four indolo[2,3-b]quinoxalin-2-yl)(phenyl)methanone derivatives by cyclocondensation. The photophysical studies of dyes in various solvents and neat solid film exhibit typical electronic spectra with inbuilt intramolecular charge transfer (ICT) (λmax: 397–490 nm) confirming donor–acceptor architecture. Herein, dyes fluoresce in the blue-orange region (λEmax: 435–614) on excitation at their ICT maxima in toluene, ethyl acetate, chloroform, DMSO, and neat solid film. Two dyes, which exhibit good emission intensity in all mediums, were studied for aggregation-induced emission (AIE) effect. Electrochemical studies indicate the dyes possess relatively low lying LUMO (− 3.65 to − 3.98 eV) comparable to reported n-type/electron-transporting materials. The HOMO and LUMO energy levels were evaluated by DFT and TD-DFT calculations. TGA analysis shows the dyes exhibit good thermal stability. The characteristic optoelectronic properties and thermal stability signify these dyes are potential candidates for their application in optoelectronics. [ABSTRACT FROM AUTHOR]

Three novel donor-acceptor molecules comprising the underexplored pyridazine (Pydz) acceptor moiety have been synthesized and their structural, electrochemical and photophysical properties thoroughly characterized. Combining Pydz with two phenoxazine donor units linked via a phenyl bridge in a meta configuration (dPXZMePydz) leads to high reverse intersystem crossing rate kRISC = 3.9 · 106 s−1 and fast thermally activated delayed fluorescence (TADF) with

Two donor–acceptor conjugated copolymers comprised of a novel dithienophosphole (DTP) as the acceptor unit and bithiophene (BT) or decylthiophenebenzodithiophene (DTBDT) as the donor unit were synthesized and characterized to elucidate the relationship between donor–acceptor (D–A) architecture and organic field-effect transistors (OFETs) performance. These characteristics of D–A copolymers were affected by the structural suitability of donor and acceptor units. Poly(DTP-BT) had an ordered structure that facilitated charge carrier transfer. The crystallinity of poly(DTP-BT) increased as annealing temperature ( T ann ) increased. In contrast, poly(DTP-DTBDT) was amorphous regardless of T ann due to the long alkyl chains of the DTBDT units. OFET devices made with poly(DTP-BT) and annealed at 200 °C exhibit a highly crystalline morphology and a relatively high field-effect mobility (4.9 × 10 −3 cm 2 /(V·s)). [ABSTRACT FROM AUTHOR]

• Small donor–acceptor (D–A) based 2,3-di(pyridin-2-yl)quinoxaline amine derivatives are synthesized. • Dyes exhibit ICT transition and emits in blue to yellow region in solution. • Positive solvatochromism in dyes evaluated by E T (30), MC−Rae and weller's plots. • Dyes offer small electrochemical band gap (1.73 to 2.23 eV) and ambipolar charge transfer. • Molecules have excellent thermal stabilities. We herein report the design and synthesis of six new donor–acceptor (D–A) type, bipolar compounds containing 2,3-di(pyridin-2-yl)quinoxaline as an acceptor and diaryl/heterocyclic amine donors prepared by palladium catalyzed Buchwald‒Hartwig coupling reaction. The synthesized compounds have been characterized by different spectroscopic techniques, electrochemical analysis and thermal method. Further, the structure of compound 4 was confirmed by single crystal X −ray analysis. The characteristic absorption (λ max) with ICT feature and emission maxima (λ emm) in various solvents of 2 – 7 are found in the range of 389–440 nm and 460–555 nm, respectively, with stoke's shift within 3664−6945 cm−1. The positive solvatochromism due to solvent polarity observed in dyes confirmed by the Mc−Rae and Weller's plots. The dyes 2 – 7 show cyan blue to orange emission (λ emm = 493–581 nm) in solid film. The cyclic voltammetry (CV) was used to analyze the HOMO and LUMO energy levels of the molecules and further it was correlated by density functional theory (DFT) calculations. The excellent thermal stability and opto-electronic properties warrants the application of these dyes in opto−electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbazole based Donor–Acceptor derivatives are synthesized. • ICT transition and emission varied with modulation in acceptor units. • Excellent solvatofluorochromism with "Blue to orange" emission in solution and solid state exhibit by dyes. • Some dyes possess outstanding AIE properties by stable emissive nanoparticles formation. • Dyes offers electron transporting characteristics and small ΔE ST. In order to demonstrate an effect of varying acceptor unit on optoelectronic properties of Donor–Acceptor (D–A) assembly, we herein designed and synthesized C–N coupled, carbazole based dyes 1 – 8 by employing Buchwald–Hartwig coupling amination reaction and fully characterized by spectroscopic methods. Presence of intramolecular charge transfer (ICT) transitions (λ max = 403–467 nm) in absorption spectra of all dyes reminiscent D–A assembly in it and emit in blue–yellow region (λ emm = 467–565 nm) in solution state with marked positive solvatochromism. The photophysical studies of some of the dyes in different THF/water mixtures revealed aggregation-induced emission (AIE) feature with the nanoparticles formation, as confirmed by dynamic light scattering (DLS) technique. The HOMO (−5.42 to −5.74 eV) and LUMO (−3.03 to −3.50 eV) energy level of these molecules measured by cyclic voltammetry suggest electron transporting property in it. Further, DFT/TDDFT calculation of dyes, indicate quite comparable theoretical and experimental photophysical and electrochemical data. Moreover, calculated singlet (S 1) and triplet (T 1) excitation energy levels by DFT/B3LYP/6–311 G+(d,p) shows small ΔE ST value for some dyes and hence called as TADF emitters. Thus obtained all optoelectrochemical properties of dyes propose its potential use in optoelectronic devices and in biosensing. [ABSTRACT FROM AUTHOR]