Mechano-CPL effect: chiral difluoro-boron β-diketonate complexes show concomitant changes of emission color as well as solid state chiroptical properties upon mechanical stimulation.

The mechanoresponsive behaviora nd photochemical response of an ew bis(cyanostyryl)benzene fluorophore (CSB-5) were investigated. Green fluorescencew ith l em,max of 507 nm was found for CSB-5 in chloroform solution, mirroring the behavior of ap reviously reported similar dye (CSB-6). Alternatively,c rystalline samples of CSB-5 exhibited orange fluorescence with l em,max of 620 nm, attributable to excimer emission. Althought he emission color change was not clearly noticeable by naked eye, CSB-5 exhibited mechanochromic luminescence, due to transformation into the amorphouss tate upon grinding the crystalline powder.Interestingly,r ubbedf ilms of CSB-5 preparedo ng lass substratese xhibited ap ronounced emission color change from oranget og reen when exposed to UV light. This response is the result of ap hotochemical reaction that occursi nt he amorphous state and which causes ad ecrease of the excimer emission sites so that the emission color changes from excimer to monomer.T he crystalline material did not display such ap hotoinduced emission colorc hange and the difference in photochemical reactivity between crystalline and amorphous states was exploited to pattern the emission color of rubbed films.

We synthesized two bichromophoric difluoroboron‐β‐diketonates (DFB) connected in para and meta positions by using cyclohexane diamine as a chiral bridge (para and meta (R/S)‐CyDFB). TD‐DFT calculations revealed that the variation in connectivity of the DFB units leads to different spatial arrangements and a chirality inversion of the bichromophoric DFB. Higher gabs values were obtained in (R/S)‐CyDFB connected in para as compared to meta position. Aggregation of para (R/S)‐CyDFB in mixture of solvents increase the glum values as compared to its monomeric form. Ultrasonication and heating induced the formation of highly ordered nano‐helical wires of para (R/S)‐CyDFB that increased the glum values to 0.015. On the other hand, meta (R/S)‐CyDFB failed to form highly ordered self‐assembled wires due to hindered H‐binding sites. These observations indicate that the chiroptical properties of DFB bi‐chromophore system can be modulated with self‐assembly and spatial arrangement of the chromophores.

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Abstract:A novel palladium(II) complex with a glycoconjugated 2-(2-pyridyl)thiazole ligand was synthesized. Single-crystal X-ray analysis revealed a packing structure that may be stabilized by hydrogen bonding between sugar moieties and between methanol (crystal solvent) and a sugar moiety.