Syntheses, X-ray Crystal Structures, and Optical, Fluorescence, and Nonlinear Optical Characterizations of Diphenylphosphino-Substituted Bithiophenes

Abstract

A series of bithiophene derivatives that are either symmetrically disubstituted with two Ph(2)(X)P groups (X = O, S, Se) or monosubstituted with one Ph(2)(X)P group (X = O, S, Se) and an organic functional group (H, CHO, CH(2)OH, CO(2)Me) have been synthesized. The X-ray crystal structures of Ph(2)(Se)P(C(4)H(2)S)(2)P(Se)Ph(2), Ph(2)(O)P(C(4)H(2)S)(2)H, Ph(2)(S)P(C(4)H(2)S)(2)H, and Ph(2)(O)P(C(4)H(2)S)(2)CH(2)OH exhibit very different solid-state structures depending on the type of intermolecular π-π interactions that occur. The compounds have been characterized by electronic absorption and fluorescence studies. Of particular interest is that the quantum yields of Ph(2)(O)P(C(4)H(2)S)(2)H, Ph(2)(O)P(C(4)H(2)S)(2)P(O)Ph(2), Ph(2)(O)P(C(4)H(2)S)(2)CO(2)Me, and Ph(2)(O)P(C(4)H(2)S)(2)CH(2)OH are significantly larger than that of bithiophene (factors of 13, 14, 14, and 22, respectively). This behavior is quite different from that of analogously substituted terthiophenes in which substitution results in only modest increases in the quantum yields over that of terthiophene (factors of 0.94, 2.7, 1.3, and 1.5, respectively). DFT studies of the emission process suggest that modifying the Ph(2)(X)P group affects both the fluorescence and nonradiative rate constants while modifications of the organic substituents primarily affect the nonradiative rate constants. The higher quantum yields of the substituted bithiophenes make them promising for application in organic light-emitting devices (OLED). The optical power limiting (OPL) performances of these Ph(2)(X)P-substituted bithiophenes were evaluated by nonlinear transmission measurements in the violet-blue spectral region (430-480 nm) with picosecond laser pulses. The OPL performances are enhanced by heavier X groups and when by higher solubilities. Saturated chloroform solutions of Ph(2)(O)P(C(4)H(2)S)(2)H and Ph(2)(S)P(C(4)H(2)S)(2)H exhibit significantly stronger nonlinear absorption than any previously reported compounds and are promising candidates for use in broadband optical power limiters.

Synthesis, Linear, and Nonlinear Optical Properties of Phosphonato‐Substituted Bithiophenes Derived from 2,2‐Dimethyl‐1,3‐propanediol

“…These values are also very similar to that of PhP(Se)[ O (CH 2 ) 3 O ] (| 1 J PSe | = 876 Hz) indicating that replacing a phenyl group with a bithienyl group only slightly reduces the s‐character of the phosphorus. This behavior is analogous to that which has been observed with Ph 2 P(Se)Ar systems [Ar = Ph, | 1 J PSe | = 732; Ar = H(C 4 H 2 S) 2 , | 1 J PSe | = 735 Hz] , . The | 1 J PSe |s of pdP(Se)T 2 H and pdP(Se)T 2 P(Se)pd are larger than those of Ph 2 P(Se)T 2 H and Ph 2 P(Se)T 2 P(Se)Ph 2 (735 Hz and 739 Hz, respectively) and are slightly smaller than those of the bpP(Se)T 2 H and bpP(Se)T 2 P(Se)bp , .…”

“…The conformation of the major component in both compounds is the anti‐periplanar conformation (≈ 83 %). Both syn‐periplanar and anti‐periplanar conformations are observed for bithiophenes monosubstituted with phosphines, …”

“…We have recently reported that solutions of diphenylphosphino‐substituted oligothiophenes of the types Ph 2 P(X)T n H and Ph 2 P(X)T n P(X)Ph 2 (X = O, S, Se; T = 2,5‐C 4 H 2 S; n = 2, 3) exhibit NLA at wavelengths across the violet‐blue spectral region . The NLAs of Ph 2 P(X)T 3 H and Ph 2 P(X)T 3 P(X)Ph 2 were limited by the compounds' relatively high linear absorptions in the violet‐blue region.…”

Synthesis, thermal analysis, and linear and nonlinear optical characterization of substituted polyphosphonates derived from 1,12-dodecanediol

“…Our research group has recently reported that solutions of phosphine‐substituted bithiophenes and terthiophenes of the types Ph 2 P(X)(C 4 H 2 S) n P(X)Ph 2 and Ph 2 P(X)(C 4 H 2 S) n H (X = O, S, Se; n = 2, 3) show strong narrow band NLA at wavelengths across the violet‐blue spectral region . The phosphine‐substituted bithiophenes are particularly impressive because they combine strong NLA with high solubilities and high linear transmittances at wavelengths from 420 to 480 nm.…”

“…Finally, UV/visible and fluorescence spectroscopies have been used to evaluate the linear optical properties of solutions of the 2,2′‐bithienyl‐5‐yl substituted polyphosphonates, and the nonlinear optical properties have been evaluated using nonlinear transmittance measurements at 430 nm with a 27 ps laser pulse. The results from these studies are compared with those from our previous studies of molecular phosphonate‐substituted thiophenes …”