Syntheses of NLO diamino chromophores containing imidazole and thiophene rings as conjugation linkage

Abstract

Organic molecules with large first hyperpolarisabilities (β) have attracted considerable attention over the last 20 years for their potential applications in optical data storage, telecommunications and optical signal processing. 1,2 It is already well known that molecules containing electron-donor and electron-acceptor groups linked by a large conjugated framework possess large values of β. 3 Molecular nonlinearities can be significantly enhanced by increasing the donor and acceptor strength or the length of the conjugation pathway. 4 For example, compounds 1 and 2 shown in Scheme 1, represent the highest value of µ g β 0 (510.8 × 10 -48 /esu, 800.4 × 10 -48 /esu). 5 Although significant progress has achieved in the design and syntheses of such one dimensional dipole chromophores, 6,7 in order to make a useful device, NLO chromophores must be incorporated into a fabric version, such as poled polymers, LB films, self-assembled or crystal environments, etc. Among these, chemical incorporation of chromophores into a polymer backbone is probably the most important choice. Thus the NLO chromophores that bear reactive groups and can be covalently banded into a suitable molecular structure are greatly demanded. Up to now, only a few such chromophores have

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

“…Wu et al utilized 4,5-bis(4-aminophenyl)imidazole as a suitable donor moiety for the construction of the nitro C2-substituted imidazole push–pull systems with extended and varied π-conjugated pathway 15a – g [ 16 – 17 47 ]. The π-linker comprises 1,4-phenylene (C 6 H 4 ), thiophen-2,5-diyl (C 4 H 2 S), ethenylene, and azo subunits ( Fig.…”

“… General structure of 4,5-bis(4-aminophenyl)imidazole-derived chromophores 15a – g with various π-linkers [ 16 – 17 47 ]. …”

Synthesis and Characterization of the Ground and Excited States of Tripodal-like Oligothienyl-imidazoles

“…Therefore, approaches for improving the thermal stability of organic molecules without reducing fluorescence are needed. [2][3][4] In this respect, promising candidates are imidazole derivatives, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] as well as conjugated (oligo)thiophenes. 4,24 Organic polymeric structures are strongly dependent on marginal factors such as synthetic procedures, film morphology, poor and selective solvent solubilization, etc.…”

“…Triaryl(heteroaryl)-imidazole [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] -based chromophores have received increasing attention due to their distinctive linear and nonlinear optical properties and also due to their excellent thermal stability in guest-host systems. Besides their classical applications in medicinal chemistry, 28 2,4,5-triaryl(heteroaryl)imidazoles play also important roles in materials science due to their optoelectronic properties.…”

The influence of the relative position of the thiophene and pyrrole rings in donor–acceptor thienylpyrrolyl-benzothiazole derivatives. A photophysical and theoretical investigation

“…For the πconjugating bridge systems, several linear polyenes to various aromatic (heterocyclic) substituents have been used. [8][9][10][11] Included in these, easily delocalized five-membered rings (such as furan and thiophene based -conjugated spacers) have proved to increase the hyperpolarizabilities of NLO chromophores. 1,6,7,12,13 This is in part due to the high chemical and thermal stability together with the displayed 25 good optical properties which allow efficient -electron delocalization.…”