A Facile Synthesis of Chiral Luminescent Organoboron Polymers by Hydroboration Polymerization Utilizing Chiral Borane

Abstract

Hydroboration polycondensations of three aromatic dicyano compounds 1, 1,4-dicyanobenzene (1a), 1,3-dicyanobenzene (1b), and 1,4-didodecyloxy-2,5-dicyanobenzene (1c), with N,N,N′,N′-tetramethylethylenediamine-bis(monoisopinocampheylborane) (S-IpcBH2·TMED) were carried out to obtain optically active poly(cyclodiborazane)s (2a, 2b, and 2c) with M ns in the range from 2400 to 6800 in 61−76% yields. The hydroboration polycondensation efficiently proceeded through the complete formation of boron−nitrogen four-membered ring. The polymer structures were characterized by 1H and 11B NMR, UV−vis, photoluminescence (PL), and CD spectroscopies. Only 2c exhibited intense blue-green light emission from charge-transfer interaction by incorporation of donor and acceptor system into the polymer backbone. The emission behavior of model compounds (A and B), corresponding to polymer units of 2a and 2c, was effectively examined by theoretical calculations using the DFT method. As a result, the intense blue-green emission of 2c was observed by the bathochromic shift to a visible region. All the polymers showed intense CD signals, indicating that they formed chiral boron−nitrogen four-membered ring structure. Further, 3b and 3c were prepared by hydroboration polycondensation of 1b or 1c with R-IpcBH2·TMED. The specific rotations of 2a, 2b, and 2c showed positive values in contrast to those of 3b and 3c. The Cotton effects of the cyanobenzene moieties in 2a, 2b, and 2c at around 300−350 nm were positive, whereas the Cotton effects of the cyanobenzene moieties in 3b and 3c were negative, as were the specific rotations as well.

4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPYs) as components of novel light active materials

“…Polymers 109 as well as an analogue containing ethynyl-phenyl groups on the boron atom were found to adopt particular structures. 132 The same effect was observed for a BODIPY-containing polymer formed by a quaternary pyridinium-BODIPY (110; Fig. 56).…”

Advances in the Synthesis of Organoborane Polymers for Optical, Electronic, and Sensory Applications

“…113,114 Chiral luminescent poly(cyclodiborazanes) (33, Chart 2) were prepared using the tmeda (N,N,N′,N′-tetramethylethylenediamine) adduct of enantiomerically pure isopinocampheylborane as a precursor. 115 Polymer 33c shows a blue-green emission at 468 nm with a quantum efficiency of 18%, while polymers 33a and 33b emit only weakly in the UV. The different behavior of 33c was again attributed to charge transfer involving the electron-rich dialkoxybenzene linker.…”

Hydroboration as an Efficient Tool for the Preparation of Electronically and Structurally Diverse N→B‐Heterocycles

“…In our group, we are interested in generating the same basic structure from more readily available functional groups through classical 1,2‐hydroboration. 1,2‐Hydroboration is a mild, efficient, and atom‐economic method to introduce boryl groups into organic compounds and is increasingly used to functionalize conjugated electronic materials, or to prepare boron‐containing polymers through polyhydroboration . Regioselectivity in hydroboration reactions is primarily controlled by steric factors .…”