The Pentaphenylborole–2,6‐Lutidine Adduct: A System with Unusual Thermochromic and Photochromic Properties

Abstract

Changing color: The pentaphenylborole–2,6‐lutidine adduct 1 has unusual photophysical properties. Cooling a solution of 1 results in the disappearance of the absorption band at 578 nm and a color change from blue to yellow. Irradiation of 1 at low temperatures leads to a migration of lutidine from boron to the adjacent carbon with BC bond formation and a color change to green.

Synthesis of Zwitterionic Cobaltocenium Borate and Borata‐alkene Derivatives from a Borole‐Radical Anion

“…It should be mentioned that selective synthetic approaches to obtain borata‐alkene derivatives are relatively rare4, 32–37 and usually give highly reactive products that tend to decompose even under an inert atmosphere when isolated 33–34. Recently, our group has studied the reversible formation of a borole‐derived borata‐alkene by photolytic rearrangement of the Lewis adduct [Ph(2,6‐Me 2 C 5 H 3 N)BC 4 Ph 4 ] ( 10 ) formed by 1 and 2,6‐lutidine at low temperature (Scheme ) 6. According to UV/Vis and NMR spectroscopic data, as well as computational investigations, a photo‐induced migration of the Lewis base leads to the zwitterionic borata‐alkene derivative 11 , which converts back to 10 upon warming 6.…”

Isomerization and rearrangement of boriranes: from chemical rarities to functional materials

“…Despite the fact that photochromic switching at a boron core remains rare [36][37][38][39], there do exist several examples of photochromic systems which incorporate organoboron subunits to act as modulators of various chemical properties [40][41][42]. In particular, -BMes 2 substitution has proven to be an effective strategy for controlling the color and state-switching of DTEs via the introduction/removal of fluoride ions (F − ), which bind strongly to three-coordinated boron atoms and disrupt the π-conjugation of the molecule [43][44][45].…”

Reversible Photothermal Isomerization of Carborane‐Fused Azaborole to Borirane: Synthesis and Reactivity of Carbene‐Stabilized Carborane‐Fused Borirane

“…TheC u1-C1 distance of 1.900(4) compares to that of 1.935(8) in [CuMe 2 ] À , [18] 2.036 (4) in {1-C[NH( i Pr)]=N-( i Pr)-o-C 2 B 10 H 10 } 2 Cu, [19] and 1.920(2) in 1,1':2,2'-[Cu-(toluene)] 2 (C 2 B 10 H 10 ) 2 . [20] Theprevious result indicates that the B À C(carbene) bond in 2 is very strong and that CuCl cannot remove the carbene from the Bc enter.W ew ondered if aB rønsted acid could react with the coordinated carbene in 2.T reatment of 2 with 1equiv of HCl in ad ioxane solution afforded monochloroborane carbene adduct 4 with the cleavage of one BÀ C(cage) bond.…”

“…Generally,t he three-coordinate trigonal-planar boron center has alow-lying empty po rbital that can either form p bonding interactions, which lead to conjugated systems,oraccept the electron pair of aLewis base to afford afour-coordinate tetrahedral boron. [3][4][5][6][7] A very recent example reported by the Wang group is illustrated in Scheme 1. [1,2] Recently,o rganoboranes have been reported to display very interesting photochromism, photochemical, and thermal structural transformations.…”

“…Such unique properties of organoboranes enable promising applications in optoelectronics and colorimetric chemosensors. [8] Such photo reactions serve as am ajor method for the preparation of Lewis-base-stabilized boriranes, [3][4][5][6][7][8][9] ac lass of three-membered rings much less studied than other heteroatom-containing analogues,s uch as epoxides and aziridines. [3,4] They are usually Lewis-base-coordinated tetrahedral organoboranes.…”