Tuning the Conformation and Color of Conjugated Polyheterocyclic Skeletons by Installing ortho‐Methyl Groups

Abstract

ortho-Methyl effects are exploited to tune steric hindrance between side-chain N,N'-diaryls and polycyclic dihydrodibenzo[a,c]phenazine,a nd in turn control the conformations of N,N'-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC)a nd its ortho-methyl derivatives Mx-My( x= 0, 1o r 2, y = 1o r2 ,xand yc orrelate with the number of methyl groups in the ortho-positiond of N,N'-diphenyl). The magnitude of steric hindrance increases as xand yincrease,and the Vshaped dihydrodibenzo[a,c]phenazine skeleton is gradually tuned from abent (DPAC)toplanar (M2-M2)structure in the ground state.A saresult, the relaxation of the excited-state structure of DPAC and its numerous analogues could be mimicked by model structures Mx-My, demonstrating for the first time the the conformation change from bent-to-planar and hence al arge range of energy-gap tuning of polycyclic conjugated structures controlled by the steric hindrance.

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

“…[1][2][3][4] One popular approach is the exploitation of steric hindrance effect via anchoring bulky substituents or rigid units into molecules to increase the hindrance, stabilizing an otherwise unaffordable configuration. [5][6][7][8] Meanwhile, the 'rotational isomerism' is another strategy to fine-tune the configuration, 9,10 in which two functional moieties are connected by a designated bridge, which could be C-C single, double, triple bonds or even extended structures. [11][12][13][14][15] Accordingly, mutual arrangement of the two moieties can be altered via rotation, 16,17 bending 18 and structural reorganization [19][20][21] of the bridge such that various thermally stable configurations may exist, which purportedly exhibit different properties in terms physical or photophysical behaviors.…”

Polymer-Stretching-Regulated Microscopic Photoluminescence of Vibration-Induced Emission (VIE) Molecules

“…Along with reacting to variations in the external surroundings, such as the solvent polarity, viscosity and temperature, the VIE molecules showed diverse emissions from blue to orange red through a gradual process; such emissions are inseparable from the successive changes in their conformations. The related mechanism has been fully studied in our previous reports (28)(29)(30)(31)(32)(33)(34)(35)(36). For further exploration, this research focused on microcosmic disclosure in polymer systems by photoluminescence regulation of VIE molecules (Fig.…”

“…Vibration-induced emission (VIE) (25)(26)(27), as an emerging photoluminescence mechanism, has drawn great attention in recent years owing to its tunable multicolor mission between different successive configurations. This mechanism has been attributed to the saddle-like VIE molecules of 9,14-diphenyl-9,14-dihydrodibenzo[a,c]-phenazine and its derivatives with consecutive conformations from bent to planar (28)(29)(30)(31), resulting in appealing multicolor mission (blue and orange red) from a single molecular entity. Under different external environmental conditions, such as solvent polarity (32,33), viscosity (34,35) and temperature (36), VIE molecules display excellent photoluminescence properties with favorable reversibility and controllable regulations (37,38).…”

Vibratile Dihydrophenazines with Controllable Luminescence Enabled by Precise Regulation of π-Conjugated Wings

“…[17][18][19][20] Studies on these dynamic fluorescent π-systems allow us to further understand the relationship between π-conjugated structures and photophysics and provide possibilities to fabricate new organic functional materials in the future. Theoretical and experimental studies of sterically hindered dihydrophenazines, e.g., DHP-1 6 and DHP-2 17,21 (Figure 1) composed of phenanthrene or pyrene and benzene fused on a dihydropyrazine ring, have led to a clear understanding of the skeletal planarization process, including the influences of structural elements (e.g., molecular symmetry 6 and conformational modulation 22,23 ) on the photophysical properties. On the one hand, the structural changes of these molecules occur mainly on the side substituents at the N atoms, and the simple structures of the fused flapping wings fail to provide sufficient information on the relationship between the size of the flapping wings and the photophysical properties.…”