Diphenylaminofluorene-Based Two-Photon-Absorbing Chromophores with Various π-Electron Acceptors

Abstract

A new series of linear, asymmetrical diphenylaminofluorene-based chromophores (AFX) with various strong π-electron acceptors were synthesized and evaluated for two-photon absorptivity. These chromophores were studied to determine a suitable replacement for 2-(4-vinyl)pyridine, the π acceptor for our previously reported AFX series, which contains a photochemically and thermo-oxidatively unstable olefinic unit. In addition to the benzoyl group (AF-370), these π-electron acceptors include 2-benzothiazolyl (AF-240), 2-benzoxazolyl (AF-390), 2-(N-phenyl)benzimidazolyl (AF-386), and 2-(3,4-diphenyl)imidazolyl (AF-385) moieties (five-membered heterocycles) and the 2-quinoxalinyl (AF-260) group (six-membered heterocycle). From nanosecond nonlinear transmission measurements, these new chromophores have effective two-photon cross sections (σ2‘) at 800 nm, spanning from 3.87 × 10-48 cm4 s/(photon molecule) for AF-385 to 97.46 × 10-48 cm4 s/(photon molecule) for AF-240. Two of them, 2-benzothiazolyl-end-capped AF-240 and benzoyl-containing AF-370 [σ2‘ = 84.32 × 10-48 cm4 s/(photon molecule)] stand out as having relatively good, albeit lower, values of two-photon cross sections, as compared to that of previously reported N,N-diphenyl-7-[2-(4-pyridinyl)ethenyl]-9,9-didecyl-fluorene-2-amine, AF-50 [σ2‘ = 115.6 × 10-48 cm4 s/(photon molecule)]. However, we observed that AF-240 was more photochemically robust than AF-50 when their THF solutions were subjected to repetitive and prolonged exposure to nanosecond laser radiation. Finally, on the basis of our nanosecond TPA cross-section data (σ2‘/MW values), the general trend for π-electron accepting ability, i.e., ability to accept charge transferred from diphenylamine appears to be as follows: 2-(4-vinyl)pyridine > 2-benzothiazolyl > benzoyl > 2-(N-phenylbenzimidazolyl > 2-quinoxalinyl > 2-benzoxazolyl > 2-(4,5-diphenyl)imidazoyl.

Electroluminescence Characteristics of a New Green-Emitting Phenylphenothiazine Derivative with Phenylbenzimidazole Substituent

“…[9][10][11] Furthermore, the heteroaromatic rings are directly boned to a donor to facilitate maximal coplanarity between the donor and the acceptor, which is crucial for the efficient charge transfer in the molecules. 12 Phenothiazines have been intensively investigated as a donor in electrogenerated chemiluminescence (ECL) systems, because of their highly stable radical cations, unique nonplanar geometry, and low reversible oxidation potential. 13,14 The studies of OLEDs based on phenothiazinecontaining D-A molecules have already been reported.…”

Synthesis of novel benzothiazole compounds with an extended conjugated system

“…Excess dibromide was separated from product by column chromatography on silica gel with hexane as eluent and the product was eluted with ethyl acetate/ hexane (1:20). Evaporation of the solvent gave the title compound 9 (4.42 g, 60 %) as a white solid, 35 4,4'-(12,12'-Disulfanediylbis(dodecane-12,1-diyl)bis(oxy))dibenzaldehyde (10). Hexamethyldisilathiane [(Me 3 Si) 2 S] (0.435 g, 2.5 mmol) was added to the stirred solution of 4-(12-bromododecyloxy)benzaldehyde 9 (0.740, 2 mmol) in dry THF (10 mL) at -10 °C.…”

“…[3][4][5][6][7][8][9] The benzothiazolyl unit is an excellent acceptor that gives rise to donor-π-acceptor (D-π-A) type compounds. [10][11][12] Benzothiazolyl derivatives have much better chemical, thermal, and photochemical stabilities than structurally similar compounds. 10 2-(3,5,6-Trifluoro-2-hydroxy-4-methoxyphenyl) benzothiazole with a zinc cation is used for fluorescent probe sensing.…”

“…[10][11][12] Benzothiazolyl derivatives have much better chemical, thermal, and photochemical stabilities than structurally similar compounds. 10 2-(3,5,6-Trifluoro-2-hydroxy-4-methoxyphenyl) benzothiazole with a zinc cation is used for fluorescent probe sensing. 13 Bis-[2-(2-hydroxyphenyl)benzothiazolate]zinc [Zn(BTZ)2] is one of the best white electroluminescent materials used in organic light-emitting diodes (OLEDs).…”

Synthesis, Characterization of a Novel Conjugated Structural Oligomer

“…Contributed by many scientists and research groups, numerous Type II and some Type III MPA active compounds were successfully synthesized [16][17][18][19] and characterized in the past two decades as investigation of MPA structureproperties relationship. The π-bridges could be unsaturated aliphatic chains or aromatic ring which connected the acceptor(such as: triazine, triphenylamine) and donors (such as, nitrogen-containing heterocyclic aromatic groups).…”