Excited state aromatization assisted push-pull abilities of two unsaturated oxazolone derivatives

Peculiarities of supramolecular organization of cyclic ketones with vinylacetylene fragments

“…Similar cycloalkanones connected with heterocycles through double bonds also form dimer architectures in their crystals. Dimers connected through four C-HÁ Á ÁO hydrogen bonds have been found in (furan-2-yl)methylidene connected with 1,3-oxazol-5(4H)-one (Karabıyık et al, 2017), 2,5-bis(furan-2-ylmethylene)cyclopentanone (RUGLUB01; Schweizer & Abdel-Rahman, 2017) and 2,6-difurfurylidenecyclohexanone (XOZWOZ; Ma et al, 2009), although such motifs are absent from symmetrical 2,6bis(2-furylmethylene)-4-methylcyclohexanone (CAKHAA; Abdel-Rahman & Hussein, 2013) and another polymorph of 2,5-bis(furan-2-ylmethylene)cyclopentanone (RUGLUB; Ma et al, 2009). Besides dimer formation, the carbonyl O atom in these compounds is able to take part in additional hydrogen bonding, which allows the realization of chain and layer motifs.…”

Photo-Induced Partially Aromatized Intramolecular Charge Transfer

“…1 H NMR (400 MHz, CDCl 3 ): δ 9.26 (s, 1H), 8.30 (d, J = 8.4 Hz, 1H), 7.83 (dd, J = 8.4, 7.0 Hz, 1H), 7.64−7.58 (m, 7H), 6.79 (s, 1H). 13 13 C NMR, 19 F NMR, COSY, and HSQC spectra for derivative 3g can be found in Figures S1 to S6 in the Supporting Information material.…”

“…However, it is interesting to highlight that most of these dual-emissive dyes are incompatible with the ICT models bearing a pseudo-aromatic ring in a rigid structure (Chart c), − which opens the door to the occurrence of an ICT process dependent on the aromatization or partial aromatization of the pseudo-aromatic ring as an (A) moiety, which is a suitable process to stabilize the electronic distribution of the excited state and generate a stable charged state (CT). It is well known that the gain of aromaticity confers stability to nonaromatic molecules, and it tends to be a favorable process from the thermodynamic point of view. − Also, the dearomatization is highly favored to form a nonaromatic ring upon excitation or specific chemical conditions, but unstable aromatic systems are preferred for this case. − Some experimental and theoretical studies on pseudo-aromatic fulvenes, oxazolones, and annulenes have demonstrated that aromatization helps in stabilizing the electronic configuration of their excited states with the generation of the aromatic excited state. − Also, changes in the aromaticity profile between the ground state and the excited state offer advantages for elucidating ICT mechanisms related to aromatization because evident geometric and electronic changes are usually generated between an aromatic and nonaromatic state . It can be monitored by optical and transient spectroscopic analysis as well as by robust theoretical calculations. , Then, taking advantage of the role of aromaticity in the stabilization of excited states, herein we report a novel ICT model named partially aromatized intramolecular charge transfer (PAICT), which permits to visualize the phenomenon of charge transfer in fused-heterocyclic dyes beyond the popular TICT or PICT schemes.…”