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Design and synthesis of novel mono- and dimeric quinazoline derivatives (+)-6-methyl-6-pyridin-2-yl-5,6-dihydrobenzo[4,5]imidazo[1,2- c ]quinazoline ( 1 ) and (+)-6-[(6-methyl-5,6-dihydrobenzo-[4,5]imidazo[1,2-c]quinazolin-6-yl)-pyridin-2-yl]-6-methyl-5,6-dihydro-benzo-[4,5]imidazo-[1,2- c ]quinazoline ( 2 ) have been described. Both 1 and 2 have been characterized by elemental analyses, FT-IR, 1 H and 13 C NMR, HRMS spectroscopic studies and their structures authenticated by X-ray single crystal analyses. Photophysical properties of these compounds have been studied by UV/VIS absorption and fluorescence spectroscopy and transient photoluminescence analysis in solution, powder, and non-doped (neat) and doped vacuum-deposited films. A broad emission spectrum spanning most of the visible range and good thermal stability indicated promising application of 1 and 2 as OLED emitters. Unfortunately, under current flow we observed rapid device degradation, presumably to be related to free –N H moiety in these compounds. [ABSTRACT FROM AUTHOR]

Meticulous attention to details of intramolecular charge transfer (ICT) has proved to be an effective strategy to design donor-acceptor fluorophores equipped with multichromic behaviour. Herein, we report three asymmetric donor-acceptor fluorophores bearing A′−D−A−D−A′ and D′−D−A−D−D′ scaffolds. The D−A−D core has been modified by appending pyridine/pyrimidine as additional acceptor and phenyl as additional donor and piperazine as flexible spacers. The asymmetric scaffold has equipped them with naked-eye solvatochromism even under daylight which further authenticated the effective charge separation in ground as well as excited state. The comparative account of photophysical behaviour displays the varying extent of twisted intramolecular charge transfer (TICT) owing to asymmetry. The interplay of restricted intramolecular rotation (RIR) and TICT leads to AIE induced H+ sensing and reversible acidochromism in PC1 which can be visualized by a comparatively uncommon acid induced emission enhancement. The activation of vibrational bands at higher temperature leads to a rare temperature induced emission enhancement in PC1−PC3. PC1 has been developed as the very first 'turn-on' thermochromic sensor based on β-diketone-boron difluoride (BF 2 bdk) complexes. [Display omitted] • The present work describes the synthesis of β-diketone-boron difluoride (BF 2 bdk) based asymmetric donor-acceptor complexes. • These asymmetric D-A molecules show competitive charge transfer pathways depending upon the type of modification. • The most significant outcome can be visualized in form of visible solvatochromism. • These further display AIE induced H+ sensing and reversible acidochromism. • The activation of vibrational bands at higher temperature leads a rare temperature induced emission enhancement. [ABSTRACT FROM AUTHOR]