Investigation of thermal and luminescent properties in 4,7-diphenylethynyl-2,1,3-benzothiadiazole systems

ABSTRACT

A series of luminescent liquid crystals based on 4,7-diphenylethynyl-2,1,3-benzothiadiazole system was prepared and characterised. The molecules were planned varying number, length and position of the linear alkoxy/thioalkyl chains. Their mesomorphic properties were studied by differential scanning calorimetry, polarised optical microscopy and X-ray diffraction. The liquid crystalline properties were found to be dependent on the length, position and number of the peripheral alkoxy chains. It was observed preferentially smectic C and nematic phases whose stability increase with the elongation of the peripheral portion. Photophysical studies were performed in chloroform solution. These compounds displayed strong yellow photoluminescent properties in the visible region, with absorption patterns peaking around 400–450 nm and emission between 500–610 nm with good quantum yields. Also, solvatochromism studies were performed.

Graphical Abstract

KEYWORDS:

• 2-benzothidiazoles
• luminescence
• liquid crystals
• organic synthesis

Acknowledgements

The authors thank the following institutions for financial support: CNPq (MCTI/CNPq Nº 14/2014 - Universal) and FAPESB (PIBIC). The authors thank prof. Dr Silvio Cunha and Mauricio Moraes Victor from UFBA for providing free access to reagents and optical equipments. The authors are also thankful to CEBIME-UFSC for the HRMS analysis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the CNPq and Fundação de Amparo à Pesquisa do Estado da Bahia (PIBIC).