Tunable circularly polarized luminescence of sol-gels based on chiral cyclometalated platinum(II) complexes

Two couples of enantiomeric pinene-containing N boolean AND C boolean AND N and C boolean AND N boolean AND N-coordinated Pt(II) isocyanide complexes decorated with long alkyl chains have been prepared and characterized. Complexes (-)-1 and (-)-2 form chiral ordered self-assemblies through Pt...Pt, pi-pi , and hydrophobic-hydrophobic interactions in nonpolar solvents, which is manifested by scanning electron and confocal microscope studies. Complexes (-)-1 and (-)-2 display appreciable aggregation-induced emission enhancement behavior in the CH2Cl2/n-hexane system with the emission quantum yield (Phi(em)) intensified by a factor of twenty. The complexes exhibit thermo-responsive sol-to -gel transition and solvent-tuned emission colors in higher alcohols or alkane solvents. Considerable circularly polarized luminescence (CPL) signals deriving from chiroptically active (MMLCT)-M-3 transition with the glum value of 10-2 order have been found for most sols at RT. Despite minor structural variations in complexes (-)-1 and (-)-2 , the CPL activity of Pt(N boolean AND C boolean AND N) isocyanide complex (-)-1 is more sensitive to solvent and temperature. In contrast, the CPL activity of Pt(N boolean AND N boolean AND C) isocyanide complex (-)-2 is inert to external factors. This research provides a new design strategy for developing tunable CPL platinum(II) complex sol-gels.

Automated summary

This study successfully synthesized two pairs of enantiomeric pinene-containing Pt(II) isocyanide complexes and demonstrated their ability to form chiral ordered self-assemblies in nonpolar solvents. Additionally, these complexes exhibited aggregation-induced emission enhancement behavior in specific solvents and showed tunable emission colors and aggregation states by controlling the solvent and temperature.