Ultraviolet and Infrared Spectra of Diboron in Solid Neon at 4 K

Abstract

Apart from products H, B, BH, BH and BH identified from their emission spectra in the UV/Vis region, photolysis of diborane(6) dispersed in solid neon at 4 K with far-ultraviolet light from a synchrotron led to observation of absorption line (0,0) of the electronic transition A Σ ←X Σ of B at 326.39 nm. Absorption lines (1,0) of B , B B and B were recorded at 316.63, 316.40 and 316.15 nm, respectively. ΔG of state A Σ for B , B B and B in solid neon are accordingly derived to be 945, 968 and 993 cm , respectively. Weak lines (0,1) of B at 29586 cm and of B B at 29560 cm , corresponding to 1042±30 and 1068±30 cm for vibrational modes in the electronic ground state, were recorded in emission. An absorption line recorded at 1066.5±0.5 cm in infrared spectra after photolysis of either B H in Ne or B D with D in Ne is thus attributed to B B.

Identification of cyc-B3H3 with Three Bridging B–H–B Bonds in a Six-Membered Ring

“…Our difference spectra are derived upon subtracting the spectra recorded after irradiation from the spectrum before irradiation; in these spectra, the lines pointing upward indicate production and the lines pointing downward indicate destruction. In addition to the infrared absorption lines assigned previously, 11,12 the lines in sets with similar temporal profiles of production appeared after photolysis at specific selected wavelengths, which we discuss here.…”

“…In experiments involving the irradiation of diborane (6) dispersed in solid neon near 4 K with tunable far-ultraviolet (FUV) light from a synchrotron, we identified, among various new lines in infrared absorption spectra after photolysis, signals assigned to several boron hydrides, including BH, BH 2 , BH 3 , B 2 H 2 , and B 2 H 4 ; 11 from visible and ultraviolet spectra in emission or absorption, we assigned signals also to B, H, and B 2 . 12 A further new species is identified here on the basis of quantum-chemical calculations of vibrational wavenumbers and intensities of several isotopic variants, as cyc-B 3 H 3 (D 3h ) in a singlet electronic state, which features three bridging B−H−B bonds in a novel six-membered ring. Such a structure has no precedent among diverse boron hydrides or even hydrides of other elements.…”

“…In experiments involving the irradiation of diborane(6) dispersed in solid neon near 4 K with tunable far-ultraviolet (FUV) light from a synchrotron, we identified, among various new lines in infrared absorption spectra after photolysis, signals assigned to several boron hydrides, including BH, BH 2 , BH 3 , B 2 H 2 , and B 2 H 4 ; 11 from visible and ultraviolet spectra in emission or absorption, we assigned signals also to B, H, and B 2 . 12…”

“…An exploration of the spectra of not only compounds stable at 300 K but also the radicals and intermediate species that can be trapped in inert environments provides fascinating new knowledge about their structures, from which concepts of bonding are developed. In experiments involving the irradiation of diborane(6) dispersed in solid neon near 4 K with tunable far-ultraviolet (FUV) light from a synchrotron, we identified, among various new lines in infrared absorption spectra after photolysis, signals assigned to several boron hydrides, including BH, BH 2 , BH 3 , B 2 H 2 , and B 2 H 4 ; from visible and ultraviolet spectra in emission or absorption, we assigned signals also to B, H, and B 2 …”