Upon mechanical stimulation, 9-anthryl gold(I) isocyanide complex 3 exhibited a bathochromic shift of its emission color from the visible to the infrared (IR) region, which is unprecedented in its magnitude. Prior to exposure to the mechanical stimulus, the polymorphs 3α and 3β exhibit emission wavelength maxima (λ) at 448 and 710 nm, respectively. Upon grinding, the λ of 3α and 3β are bathochromically shifted to 900 nm, i.e., Δλ (3α) = 452 nm or 1.39 eV. Polymorphs 3α and 3β thus represent the first examples of mechanochromic luminescent materials with λ in the IR region.

Abstract:The first Dimesitylboryl substitution of aryl halides with a silylborane bearing a dimesitylboryl group in the presence of alkalimetal alkoxides is described. The reactions of aryl bromides or iodides with Ph2MeSi-BMes2 and Na(OtBu) afforded the desired aryldimesitylboranes in good to high yields and with high borylation:silylation ratios. Selective reaction of the sterically lesshindered C−Br bond of dibromoarenes provided monoborylated products. This reaction was used to rapidly construct a D-π-A dimesitylarylborane with a non-symmetrical biphenyl spacer.Boron-containing π-conjugated compounds have received considerable attention as an important class of organic materials [1] with uses such as emissive materials, [2] two-photon absorption materials, [3] ion sensors, [4] electron-transporting materials, [5] and nonlinear optical materials.[6] The unique optical properties of these compounds arise from the pπ-π* conjugation between the vacant p-orbital of the boron atom and the π* orbital of the attached carbon π-conjugated moieties. A dimesitylboryl (BMes2) group has been employed in most of these compounds because of its strong π-electron accepting ability and air stability. The routes to access aryldimesitylborane are highly limited despite considerable efforts to develop methods to synthesis organoboron compounds. [7][8][9][10] The most popular synthesis of aryldimesitylboranes involves nucleophilic substitution of dimesitylboryl electrophiles (Mes2BX, X = halogen or OR) with organometallic compounds (ArM, M = Li, Mg). Aryldimesitylboranes are also synthesized by reaction of aryl boronic acid esters and MesLi.[11] These reactions are laborious and must be individualized for each aryldimesitylborane prepared. The use of organometallic reagents limits reaction scope and these reagents require multi-step syntheses, with low total yields (Scheme 1a). There are no direct methods to synthesize ArBMes2 from ArX. We recently reported a transitionmetal-free boryl substitution of organohalides using (phenyldimethylsilyl)pinacolborane [PhMe2Si-B(pin)] and an alkoxy base. This reaction allows the direct boryl substitution of aryl, alkyl, alkenyl and heteroaryl halides without using organometallic reagents. [12] We expected that the use of a silyl borane [13] with a diarylboryl group instead of B(pin) could provide a potent complementary method for the synthesis of triarylboranes. Herein, we report the first direct dimesitylboryl substitution of aryl halides using (diphenylmethylsilyl)dimesitylborane (Ph2MeSi-BMes2) [14] and Na(OtBu), which provides the corresponding aryldimesitylboranes in good to high yield with high borylation:silylation (B:Si) ratios (Scheme 1b). Boryl substitution of the less sterically hindered bromo group of dibromoarene substrates was highly selective and gave monoborylated products. We demonstrate the utility of this method by rapidly constructing a D-π-A dimesitylarylborane containing a nonsymmetrical biphenyl spacer.