Boron clusters as structural elements of novel liquid crystalline materials

Abstract

closo-Boranes are characterised by high thermal and oxidative stability due in part to highly delocalised bonding within a σ -framework. These boron clusters when employed as structural elements of liquid crystals give rise to novel structures with unique properties and vast potential in applications. The neutral closo-boranes such as the carboranes provide opportunity to perform fundamental structure-property relationship studies that may provide additional insight on the liquid crystalline state. The anionic closo-borates possessing a highly delocalised negative two charge can be used as structural elements of zwitterionic, quadrupolar liquid crystalline materials. Such materials may be of use for understanding the effects of polarity on the liquid crystalline state. Lastly, the anionic closo-monocarbaborates possessing a single highly delocalised negative charge can be envisioned as structural elements of either highly polar or ionic liquid crystalline materials. The highly polar materials may also serve as models for understanding the effects of polarity on the liquid crystalline state. Additionally, they should have application as positive ε additives for nematic liquid crystalline mixture formulations. The ionic materials, where the anionic fragment drives liquid crystalline behaviour, lend themselves as potential electrolytes for anisotropic ion transport in battery technologies. The review presented here introduces these concepts and highlights the current status of boron cluster containing liquid crystalline materials.

Thermotropic MIDA Boronates as a Case Study for the Role of Dipolar Interactions in Liquid Crystalline Self‐Assembly

“…For example,t ricoordinated boron compoundsa re Lewis acidic, isoelectronicw ith carbeniumions, possess p-electron-acceptor as well as inductive s-electron-donor capacity,u ndergo formation of tetracoordinate borates, and conjugate adjacent p-systems, whereas compounds containing BÀNb onds are isoelectronic with the corresponding CÀCa nalogues and displays trongl uminescence. [1][2][3][4][5][6][7] With regard to thermotropic liquid crystals, most work hasb een devoted to borondifluoride b-diketonates (or b-enaminoketonates), [8][9][10][11][12][13][14] borondipyrromethene (BODIPY) derivatives (1), [15][16][17][18][19][20][21][22][23][24][25][26][27] and boron clusters (2) [28][29][30][31][32][33][34][35] (Figure 1). In diketonate and BODIPY derivatives such as 1 or subphthalocyanines, the boron atom is surrounded by af latm esogenic p-system, which not only contributes to the liquid crystalline self-assembly,b ut also adds favorable absorption and emission characteristics.…”

Interaction of the anion [2-B₁₀H₉O(CH₂)₄O]− with secondary amines

“…Кластерные анионы бора [B n H n ] 2-(n = 10, 12) представляют собой один из уникальных примеров полностью неорганических кластеров, обладающих высокой устойчивостью к действию окислителей и склонностью к замещению экзо-полиэдрических атомов водорода на различные функциональные группы [1][2][3]. Производные на основе борных полиэдров этого класса находят все более широкое применение в науке и технике, причем одной из наиболее значимых областей остается медицинская сфера, а именно 10 B-нейтронозахватная терапия злокачественных опухолей [4][5][6][7][8][9][10][11][12][13][14]. В связи с этим очень актуальной является разработка новых методов синтеза клозо-боратов, содержащих биологически активные группы, которые также могут быть модифицированы.…”

The Mechanism of Halogenation of Decahydro-closo-Decaborate Dianion by Hydrogen Chloride

“…Functional derivatives of [B 10 H 10 ] 2− and [B 12 H 12 ] 2− closo-borane dianions are promising compounds for the application as 10 B boron carriers in boron neutron capture therapy of cancer [1][2][3][4][5][6][7], as solid-state electrolytes [8][9][10][11][12], and structural components of liquid crystals [13][14][15][16] due to their high boron content and chemical, electrochemical and thermal stability. In particular, the halogen-substituted derivatives are per-spective as weakly coordinating ions [17,18] and components of the ionic liquids [18][19][20][21].…”