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A series of ultra-efficient blue borane fluorophores

DOI: 10.1021/acs.inorgchem.0c02277 DOI Help

Authors: Jonathan Bould (Institute of Inorganic Chemistry of the Czech Academy of Sciences) , Kamil Lang (Institute of Inorganic Chemistry of the Czech Academy of Sciences) , Kaplan Kirakci (Institute of Inorganic Chemistry of the Czech Academy of Sciences) , Luis Cerdán (Consejo Superior de Investigaciones Científicas (CSIC)) , Daniel Roca-sanjuán (Universitat de València) , Antonio Francés-monerris (UniversitatdeValència) , William Clegg (Newcastle University) , Paul G. Waddell (Newcastle University) , Marcel Fuciman (University of South Bohemia) , Tomáš Polívka (University of South Bohemia) , Michael G. S. Londesborough (Institute of Inorganic Chemistry of the Czech Academy of Sciences)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry , VOL 59 , PAGES 17058-17070

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 22240

Abstract: We present the first examples of alkylated derivatives of the macropolyhedral boron hydride, anti-B18H22, which is the gain medium in the first borane laser. This new series of ten highly stable and colorless organic–inorganic hybrid clusters are capable of the conversion of UVA irradiation to blue light with fluorescence quantum yields of unity. This study gives a comprehensive description of their synthesis, isolation, and structural characterization together with a delineation of their photophysical properties using a combined theoretical and experimental approach. Treatment of anti-B18H221 with RI (where R = Me or Et) in the presence of AlCl3 gives a series of alkylated derivatives, Rx-anti-B18H22–x (where x = 2 to 6), compounds 2–6, in which the 18-vertex octadecaborane cluster architectures are preserved and yet undergo a linear “polyhedral swelling”, depending on the number of cluster alkyl substituents. The use of dichloromethane solvent in the synthetic procedure leads to dichlorination of the borane cluster and increased alkylation to give Me11-anti-B18H9Cl211, Me12-anti-B18H8Cl212, and Me13-anti-B18H7Cl213. All new alkyl derivatives are highly stable, extremely efficient (ΦF = 0.76–1.0) blue fluorophores (λems = 423–427 nm) and are soluble in a wide range of organic solvents and also a polystyrene matrix. The Et4-anti-B18H18 derivative 4b crystallizes from pentane solution in two phases with consequent multiabsorption and multiemission photophysical properties. An ultrafast transient UV–vis absorption spectroscopic study of compounds 4a and 4b reveals that an efficient excited-state absorption at the emission wavelength inhibits the laser performance of these otherwise remarkable luminescent molecules. All these new compounds add to the growing portfolio of octadecaborane-based luminescent species, and in an effort to broaden the perspective on their highly emissive photophysical properties, we highlight emerging patterns that successive substitutions have on the molecular size of the 18-vertex borane cluster structure and the distribution of the electron density within.

Journal Keywords: Reaction products,Absorption,Substituents,Alkyls,Cluster chemistry

Subject Areas: Chemistry, Materials

Instruments: I19-Small Molecule Single Crystal Diffraction