•Bpy-boronium complexes display photoinduced solid-state coloring behavior.•The substituents on the boron atom are critical to gain photoresponsive capability.•Modifying the ligand provides a wide variation in the photoinduced solid color.•A viologen-like photoredox process is suggested as a possible mechanism for coloring.Boronium complexes bearing a 9-borabicyclononane framework with a bipyridine-type ligand display photoinduced solid-state coloring behavior. While the identity of the substituents on the boron atom is critical to gain photoresponsive capability, modifying the nitrogen-containing ligand structure and its substituents provides a wide variation in the photoinduced solid color.

The extended π-electronic conjugation system of the (octaethylporphyrin)-(dihexylbithiophene)-(Lewis base) triads [OEP-DHBTh-LB] exhibits the proton-mediated reversible changes in both 1H NMR and UV–vis spectra via two-step processes, reflecting the structural features of DHBTh and LB constituents. The spectral changes of OEP-DHBTh-LB with trifluoroacetic acid (TFA) were quantitatively examined by means of 1H NMR spectral measurement and comparatively analyzed in terms of stereo-electronically controlled effects of DHBTh and LB constituents on its reversibly transformable chromatic system. Successively, based on the minimum amount of TFA necessary for completion of spectral changes at respective steps, the sensitivity and stability of OEP-DHBTh-LB to TFA were evaluated, from the viewpoint of the interactive behavior of the lone pair electrons on N atom in LB with the extended OEP constituent. The present study provides a useful guideline of the molecular design for further sophisticated OEP-based chromatic system with proton-sensing functionality.

Based on the fact that anthracene (Anth) possesses much higher similarity in electron-releasing ability to porphyrin nucleus than the other polyacenes, the dimeric octaethylporphyrin (OEP) derivatives 4 and 5 (OEP–Anth–OEP) were synthesized and their structure–property relationships were examined, as compared with related OEP dimers 1–3. Among them, the derivative 4 showed enormously high electronic communication between two terminal OEP rings, potentially providing a suitable unit of the electronic structure for molecular design of the OEP devices operating with less energy and with higher sensitivity to outside stimuli.

Tris(4-amino-2,6-dimethylphenyl)borane (1), a triarylborane bearing an unsubstituted amino group on all of its aryl substituents, and related triarylboranes were synthesized via Ullmann condensation. The facile dehydration reactions of 1 with benzaldehyde and nitrosobenzene gave tris[4-(benzylidenamino)-2,6-dimethylphenyl]borane and tris[2,6-dimethyl-4-(phenylazo)phenyl]borane, respectively. These triarylboranes bear an extended π-conjugated system bridged by a nitrogen-containing π-linker on each of their aryl groups. UV–vis absorption spectra and theoretical calculations revealed that the π-conjugated system of the triarylborane was effectively extended by utilizing the reactivity of the amino groups.

An extended π-electronic conjugation system of the 1,1′-bis[p-(N,N-dimethylaminophenyl)butadiynyl]ferrocene derivative 1 has been synthesized, with our integrated cross-coupling reaction between the corresponding TMS-protected acetylenes in one-pot. Quantitative 1H NMR and UV–vis spectral studies of 1 have been performed, providing a methodology for molecular functions transformable by a proton-mediated reversible conformation control.

An extended π-electronic conjugation system of 1,1′-bis(diacetylene-group) connected ferrocene–thiophene derivative has been synthesized, with our integrated reaction between the corresponding TMS-protected acetylenes in one-pot. Its electronic properties have been examined, suggesting a cooperatively functional behavior of the diacetylene-group connected constituents.

The dinucleic octaethylporphyrin (OEP) derivatives described as OEP-(p-Phen)n-OEP (n=1–4) were synthesized, in each of which the porphyrin ring is spaced with p-phenylene group. Their electronic properties were studied, as compared with those of the corresponding dihexylbithiophene (DHBTh) derivatives with head-to-head (HH) and tail-to-tail (TT) orientations. It proves that OEP-(p-Phen)n-OEP possesses an in-between feature of OEP-(HH-DHBTh)n-OEP and OEP-(TT-DHBTh)n-OEP in electronic properties.