Microwave-Assisted Selective Synthesis of Mono- and Bistriazines with π-Conjugated Spacers and Study of the Optoelectronic Properties

Abstract

A series of mono- and bistriazine derivatives were selectively prepared in high yields using microwave irradiation. Donor substituents were attached on the triazine ring, including pyrazolyl-substituted anilines and o-, m-, and p-phenylenediamine as π-conjugated spacers. This method was used to build σ-π-σ-A-σ-D systems for monotriazines and D-σ-A-σ-π-σ-A-σ-D systems for bistriazines. A study of the optoelectronic properties was performed by UV-vis and fluorescence spectroscopy and cyclic voltammetry. The monotriazines do not show any emission, but the bistriazines are blue emitters and show an interesting solvatochromic effect with large Stokes shifts of more than 10,000 cm(-1) in some cases and quantum yields up to 23%. The optoelectronic properties depend on the conjugation and the position and donor character of the substituents and spacers. Cyclic voltammetry was used to determine the energy levels (HOMO and LUMO) in the bistriazines. An increase in the energy of the HOMO and a decrease in the energy of the LUMO were observed upon extending the conjugation. The title compounds showed interesting properties for use in optoelectronic devices, especially as blue emitters.

Solvent-Free Microwave-Assisted Synthesis of 2,5-Dimethoxyphenylaminotriazines

“…First, the bathochromic shift found in MeOH can be explained by the ability of this solvent to form hydrogen bonds, a situation that favors charge separation and reduces the energy gap between fundamental and excited states. However, formation of excimers is clear in CH 2 Cl 2 , which is a solvent that promotes aggregation of the triazines …”

Linear and V‐Shaped Alkynyl‐1,3,5‐tri­azines

“…The mixture was stirred at 30°C until the reaction reached completion. The reaction mixture was diluted with ethyl acetate (8 mL), and the mixture was washed with a saturated solution of NH 4 Cl (2 ϫ 15 mL). The or-ganic phase was dried with MgSO 4 and filtered, and the solvent was removed in vacuo.…”

“…1,3,5-Triazine conjugates are attracting increasing attention in materials science because of their unique optical, electrical, and optoelectronic properties. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] With the employment of C(sp 2 )-N or C(sp 2 )-O cross-coupling reactions, these heterocycles can be structurally modulated by installing various functional groups, which include pyrazolyl, [16] benzimidazolyl, [17] diphenylamino, [18] hydroxyamino, [19] carbazolyl, [20][21][22] and phenoxy substituents. [23][24][25][26][27] Recent reports reveal that the C-C bond linkage between the electron-withdrawing triazine core and chromophores exhibits excellent chemical and photochemical properties, especially within D-A (Donor-Acceptor) systems.…”

Greener approach toward synthesis of biologically active s‐Triazine (TCT) derivatives: A recent update

“…Ramirez et al [33] has described a solvent‐free and green synthesis of 2,5‐dimethoxyphenylamino‐1,3,5‐triazine derivatives (58), which have the shape like star were prepared using microwave irradiation as shown in Scheme 13. The presence of methoxy group in 2,5‐dimethoxyaniline (57) enhances donor character and improves physical properties such as optical and binding properties to act as good nucleophile.…”