Ru(0)-catalysed cross-dimerisation and -trimerisation of alkynyl- with butadienylheteroarenes

Area of Science:

• Organic Chemistry
• Photochemistry
• Materials Science

Background:

• Ruthenium catalysis enables efficient synthesis of complex organic molecules.
• π-conjugated systems are crucial for optoelectronic properties.
• Heteroaryl compounds offer unique electronic and structural characteristics.

Purpose of the Study:

• To synthesize novel di- and triheteroaryl compounds via Ru(0)-catalyzed cross-dimerization and -trimerization.
• To investigate the photochemical behavior of these synthesized compounds.
• To elucidate the structure-property relationships governing their optical characteristics.

Main Methods:

• Ruthenium(0)-catalyzed cross-dimerization and cross-trimerization reactions.
• UV-visible absorption and fluorescence emission spectroscopy.
• Time-Dependent Density Functional Theory (TD-DFT) calculations.

Main Results:

• A series of di- and triheteroaryl compounds linked by π-conjugated trienyl groups were synthesized.
• Photochemical studies revealed significant differences in absorption maxima based on the heteroaryl core.
• TD-DFT calculations and solvent effects indicated that π-system planarity, particularly in thiophene derivatives, is key to longer wavelength shifts.

Conclusions:

• The planarity of the π-conjugated system, influenced by the heteroaryl core, is a critical factor in determining the absorption and emission wavelengths.
• Cross-trimers featuring a 5-membered thiophene ring exhibit enhanced planarity and consequently, longer absorption and fluorescence wavelengths.
• These findings highlight the potential of designing π-conjugated systems with controlled planarity for tunable optoelectronic applications.