Tuning the photophysical properties of anti-B18H22: efficient intersystem crossing between excited singlet and triplet states in new 4,4'-(HS)2-anti-B18H20.
The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straightforward chemical substitution to produce 4,4'-(HS)2-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold. This subsequently enhances O2((1)Δg) singlet oxygen production from a quantum yield of ΦΔ ∼ 0.008 in 1 to 0.59 in 2. This paper describes the synthesis and full structural characterization of the new compound 4,4'-(HS)2-anti-B18H20 (2) and uses UV-vis spectroscopy coupled with density functional theory (DFT) and ab initio computational studies to delineate and explain its photophysical properties.
Thermochromic Fluorescence from B18H20(NC5H5)2: An Inorganic–Organic Composite Luminescent Compound with an Unusual Molecular Geometry
BH(NCH) is a rare example of two conjoined boron hydride subclusters of nido and arachno geometrical character. At room temperature, solutions of BH(NCH) emit a 690 nm fluorescence. In the solid state, this emission is shifted to 620 nm and intensifies due to restriction of the rotation of the pyridine ligands. In addition, there is a thermochromicity to the fluorescence of BH(NCH). Cooling to 8 K engenders a further shift in the emission wavelength to 585 nm and a twofold increase in intensity. Immobilization in a polystyrene thin-film matrix results in an efficient absorption of pumping excitation energy at 414 nm and a 609 nm photostable fluorescence. Such fluorescence from polystyrene t…
Photochromic System among Boron Hydrides: The Hawthorne Rearrangement
Photoswitchable molecules have attracted wide interest for many applications in chemistry, physics, and materials science. In this work, we revisit the reversible photochemical and thermal rearrangements of the two B20H182– isomers reported by Hawthorne and Pilling in 1966, whose mechanism had not been understood so far. We investigate the rearrangements by means of a joint experimental and computational study with the outcome that B20H182– represents the first boron-based photochromic system ever reported. Both photochemical and thermal isomerizations occur through the same intermediate and involve a diamond–square–diamond (DSD) mechanism. Given the absence within boron chemistry of named …
Distinct Photophysics of the Isomers of B18H22 Explained
The photophysics of the two isomers of octadecaborane(22), anti- and syn-B 18H 22, have been studied by UV-vis spectroscopic techniques and theoretical computational methods. In air-saturated hexane, anti-B 18H 22 shows fluorescence with a high quantum yield, Φ F = 0.97, and singlet oxygen O 2( 1Δ g) production (Φ Δ ∼ 0.008). Conversely, isomer syn-B 18H 22 shows no measurable fluorescence, instead displaying much faster, picosecond nonradiative decay of excited singlet states. Computed potential energy hypersurfaces (PEHs) for both isomers rationalize these data, pointing to a deep S 1 minimum for anti-B 18H 22 and a conical intersection (CI) between its S 0 and S 1 states that lies 0.51 e…
CCDC 1514165: Experimental Crystal Structure Determination
Related Article: Michael G. S. Londesborough, Jiří Dolanský, Luis Cerdán, Kamil Lang, Tomáš Jelínek, Josep M. Oliva, Drahomír Hnyk, Daniel Roca-Sanjuán, Antonio Francés-Monerris, Jiří Martinčík, Martin Nikl, John D. Kennedy|2017|Adv. Opt. Mater.|5|1600694|doi:10.1002/adom.201600694
CCDC 912917: Experimental Crystal Structure Determination
Related Article: Vicenta Saurí, Josep M. Oliva, Drahomír Hnyk, Jonathan Bould, Jakub Braborec, Manuela Merchán, Pavel Kubát, Ivana Císařová, Kamil Lang, and Michael G. S. Londesborough|2013|Inorg.Chem.|52|9266|doi:10.1021/ic4004559