Determination and application of the excited‐state substituent constants of pyridyl and substituted phenyl groups

Abstract

Thirty six 1‐pyridyl‐2‐arylethenes XCH=CHArY (abbreviated XAEY) were synthesized, in which, X is 2‐pyridyl, 3‐pyridyl and 4‐pyridyl and Y is OMe, Me, H, Br, Cl, F, CF3, and CN. Their ultraviolet absorption spectra were measured in anhydrous ethanol, and their wavelengths of absorption maximum λmax were recorded. Also, the 234 λmax values of 1‐substituted phenyl‐2‐arylethylene compounds (XAEY, where X is substituted phenyl) were collected. The excited‐state substituent constants σCC()pex()X of three pyridyl groups and 23 substituted phenyl groups (total of 26) were obtained by means of curve‐fitting method. Taking the λmax values of 358 samples of bi‐arylethene derivatives as a data set and 126 samples of bi‐aryl Schiff bases (including nine compounds synthesized by this work) as another data set, quantitative correlation analyses were performed by employing the obtained σCC()pex()X as a parameter, and good results were obtained for the two data sets. The reliability of the obtained σCC()pex()X values was verified. The results of this paper can provide excited‐state substituent constants for the study and application of optical properties of conjugated organic compounds containing aryl groups.

Impact of Internal Charge Transfer on the Photophysical Properties of Pyridine‐Fused Phosphorus‐Nitrogen Heterocycles

“…While the coumarin analogues of 2 b and 2 c are known, [29] no photophysical data were reported, and the other coumarins as well as the carbostyril analogues are unknown; thus, drawing conclusions to assess the effect that inclusion of the PN moiety has on the photophysical data is difficult. A recent publication from Cao and co‐workers, however, performed an extensive investigation into the photophysical properties of stilbazoles [30] . In particular, the authors analyzed para ‐substituted species that bare a marked similarity to the 3‐pyridine PNs, excluding the PN moiety (Figure 6).…”

“…A recent publication from Cao and co-workers, however, performed an extensive investigation into the photophysical properties of stilbazoles. [30] In particular, the authors analyzed para-substituted species that bare a marked similarity to the 3-pyridine PNs, excluding the PN moiety (Figure 6). Comparison of the λ abs for the parasubstituted stilbazoles to those of heterocycles 6 and 2 would indicate how attaching the PN motifs directly impact the observed absorption, versus what effect is simply a result of the donor-acceptor (DÀ A) system.…”

A new insight into the push‐pull effect of substituents via the stilbene‐like model compounds

“…The stilbene‐like model compounds (Scheme 1) were synthesized via the methods reported in our previous work [31–35], and their 13 C NMR chemical shifts δ C (X) and δ C (Y) of the carbon atoms in bridging bond CH=CH and CMe=CH were measured with a Bruker AV 500 MHz nuclear magnetic resonance spectrometer. The δ C values of the model compounds were listed in Table 1.…”

“…The model compounds A , B , and C were synthesized according to the methods of author's previous reports [31–35, 40, 41], and Seus's work [42], as shown in Figure 3. The experimental methods are as follows.…”