The Photostability of Novel Boron Hydride Blue Emitters in Solution and Polystyrene Matrix

Abstract

In recent work, the boron hydride anti-B18H22 was announced in the literature as a new laser dye, and, along with several of its derivatives, its solutions are capable of delivering blue luminescence with quantum yields of unity. However, as a dopant in solid polymer films, its luminescent efficiencies reduce dramatically. Clarification of underlying detrimental effects is crucial for any application and, thus, this contribution makes the initial steps in the use of these inorganic compounds in electrooptical devices based on organic polymer thin films. The photoluminescence behavior of the highly luminescent boron hydrides, anti-B18H22 and 3,3′,4,4′-Et4-anti-B18H18, were therefore investigated. The quantum yields of luminescence and photostabilities of both compounds were studied in different solvents and as polymer-solvent blends. The photophysical properties of both boranes are evaluated and discussed in terms of their solvent-solute interactions using photoluminescence (PL) and NMR spectroscopies. The UV degradability of prepared thin films was studied by fluorimetric measurement. The effect of the surrounding atmosphere, dopant concentration and the molecular structure were assessed.

A Window into the Workings of anti-B18H22 Luminescence—Blue-Fluorescent Isomeric Pair 3,3′-Cl2-B18H20 and 3,4′-Cl2-B18H20 (and Others)

“…Photophysical properties of some of the chlorinated derivatives of 1. As mentioned in the Introduction, compound 1 [3][4][5] and its derivatives [6][7][8][9][10][11][12][14][15][16] display various modes of useful luminescence. As such, we were keen to understand the photophysics of the new chlorinated derivatives of 1 reported here.…”

“…Laborious work involving HPLC separation and identification using mass spectrometry and UV absorption spectroscopy resulted in the imperfect isolation of an additional six chlorinated derivatives of 1. Of these six compounds, three are further isomers of dichlorinated derivatives of 1, specifically 4,4 -Cl 2 -B 18 H 20 (4), 3,1 -Cl 2 -B 18 H 20 (5), and 7,3 -Cl 2 -B 18 H 20 (6). The molecular structures of each of these isomers were established by SCXRD analyses, the results of which are shown in Figure 5.…”

“…Here, there is a renewed interest in the binary boron hydride cluster compound anti-B 18 H 22 1 due to the discovery of its utility as a new class of laser material [3]. It is also of particular interest as it fluoresces in the elusive blue region of the spectrum, with a quantum yield approaching unity [4]; it is highly photostable [3], and it is readily soluble in organic polymer matrices [3,5]. These are all factors of general practical benefit regarding the fabrication of optical devices.…”

Decaborane: From Alfred Stock and Rocket Fuel Projects to Nowadays

“…The photophysical properties of anti-[B18H22] can be tuned by the partial substitution of hydrogen atoms with various functional groups. Because of this, combined with its high stability [362][363][364][365][366], anti-[B18H22] is attracting increasing research interest, while the syn-[B18H22] isomer has received much less attention. Reprinted with permission from Ref.…”

Macropolyhedral syn-B18H22, the “Forgotten” Isomer

“…Two of the largest known macropolyhedral boranes are the isomeric docosahydrooctadecaboranes B 18 H 22 . , They exhibit a unique molecular structure with two open faces and six acidic bridging hydrogen atoms (μ H -BB). − Their structural and chemical properties, together with their interaction with light, make B 18 H 22 a promising candidate for a wide range of applications, from energy storage, , semiconductor doping ,− to nano- and optoelectronic devices. − The molecular structure of B 18 H 22 can be viewed as two decaborane molecules condensed together, with each subcluster sharing atoms B(5) and B(6) in the decaborane numbering system, in common (Figure B,C). The isomer syn -B 18 H 22 on which this study focuses is a much less-studied (“forgotten”) system compared to its anti -B 18 H 22 isomer, and it has a 2-fold symmetry axis due to the fusion of two {B10} units sharing the B(5)–B(6) edge so that B(5)B(5′) and B(6)B(6′) (Figure B); in the anti -B 18 H 22 isomer, B(5)B(6′) and B(6)B(5′), which results in the inversion symmetry (Figure C). ,, What has stimulated most of the recent interest in anti -B 18 H 22 and its substituted derivatives has mainly been their luminescence properties. − Our interest in the “forgotten”, nonluminescent isomer, syn -B 18 H 22 , has been stimulated mainly by its unique geometry and size with respect to its use as constituents of purely borane, carbon-free self-assembled monolayers and its further use toward 2-dimensional membranes with thickness below 1 nm and with a 3D-aromatic character, as well as capping ligands of atomically precise metal nanoclusters, a newly emerging class of materials with adjustable geometry, size, and properties. , …”