0000000000065985
AUTHOR
Michael G. S. Londesborough
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.
A theoretical analysis of the structure and properties of B26H30 isomers. Consequences to the laser and semiconductor doping capabilities of large borane clusters
Decaborane(14), nido-B10H14, is the major commercially available molecular building block in boron cluster chemistry. The condensation of two such {nido-B10} blocks gives the known isomers of B18H22 – a molecule used in the fabrication of p-type semiconductors and capable of blue laser emission. Here, we computationally determine the structures and thermodynamic stabilities of 20 possible B26H30 regioisomers constructed from the fusion of three {nido-B10} blocks with the three subclusters conjoined by two-boron atom shared edges. In addition, density functional theory, time-dependent (TD)-DFT and multiconfigurational CASPT2 methods have been used to model and investigate the physical and ph…
Substitution of the laser borane anti-B18H22 with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron hydrides
Reaction of anti-B18H221 with pyridine in neutral solvents gives sparingly soluble B16H18-3',8'-Py23a as the major product (ca. 53%) and B18H20-6',9'-Py22 (ca. 15%) as the minor product, with small quantities of B18H20-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive. Compound 3a is of unprecedented ten-vertex nido:eight-vertex arachno two-atoms-in-common architecture. The si…
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…
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…
A Series of Ultra-Efficient Blue Borane Fluorophores
13 pags., 14 figs., 5 tabs.
Effect of Iodination on the Photophysics of the Laser Borane anti-B18H22: Generation of Efficient Photosensitizers of Oxygen
Treatment of the laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative 7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl3 in dichloromethane, the diiodinated derivative 4,4'-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with 360 nm light, both compounds 2 and 3 give strong green phosphorescent emissions (λmax = 525 nm, ΦL = 0.41 and λmax = 545 nm, ΦL = 0.71 respectively) that are quenched by dioxygen to produce O2(1Δg) singlet oxygen with quantum yields of ΦΔ = 0.52 and 0.36 respectively. Similarly strong emissions can be stimulated via the nonlinear process of two-photon absorption when …
Unveiling the role of upper excited electronic states in the photochemistry and laser performance of: anti -B18H22
13 pags., 7 figs., -- This article is part of the themed collection: Journal of Materials Chemistry C HOT Papers
CCDC 1441506: Experimental Crystal Structure Determination
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CCDC 2009109: Experimental Crystal Structure Determination
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CCDC 2009108: Experimental Crystal Structure Determination
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CCDC 1514165: Experimental Crystal Structure Determination
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CCDC 2009112: Experimental Crystal Structure Determination
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CCDC 2009113: Experimental Crystal Structure Determination
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CCDC 1859436: Experimental Crystal Structure Determination
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CCDC 2009110: Experimental Crystal Structure Determination
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CCDC 1441507: Experimental Crystal Structure Determination
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CCDC 2009106: Experimental Crystal Structure Determination
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CCDC 2009105: Experimental Crystal Structure Determination
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CCDC 2009107: Experimental Crystal Structure Determination
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CCDC 1441504: Experimental Crystal Structure Determination
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CCDC 1859437: Experimental Crystal Structure Determination
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CCDC 1441505: Experimental Crystal Structure Determination
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CCDC 912917: Experimental Crystal Structure Determination
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