Thermal and Photophysical Properties of Highly Quadrupolar Liquid‐Crystalline Derivatives of the [closo‐B₁₂H₁₂]²⁻ Anion

Abstract

Two series of 1,12‐bis‐zwitterionic derivatives of the [closo‐B12H12]2− anion (B), containing either two 4‐alkoxypyridinium groups (1B[n]‐p) or one 4‐alkoxypyridinium and one 4‐pentylthianium groups (2B[n]‐p), were prepared and their structural (XRD, DFT), thermal, and photophysical properties were compared with those of the analogous derivatives of the [closo‐B10H10]2− anion (1A[n]‐p and 2A[n]‐p). Some 1,7‐derivatives of B were isolated and investigated. Both series 1[n] and 2[n] exhibit nematic and crystalline polymorphism; the 12‐vertex derivatives (B) have higher transition temperatures than those of the 10‐vertex analogues (A). All compounds fluoresce with quantum yields higher for 1B (ΦF=0.37 for 1B[7]‐p and ΦF=0.27 for 2B[7]‐p) than those for the 10‐vertex analogues (ΦF=0.04 for 2A[5]‐p). DFT calculations demonstrate an order of magnitude lower first hyperpolarizability, β(−ω,ω,0), for 2B[7]‐p than that for the 10‐vertex analogue 2A[7]‐p (1.7×10−30 vs. 18.9×10−30 esu at ω=0).

C(1)‐Phenethyl Derivatives of [closo‐1‐CB11H12]− and [closo‐1‐CB9H10]− Anions: Difunctional Building Blocks for Molecular Materials

“…Interestingly, in both series the substituent effect is localized and barely affects the antipodal position. The observed trend follows the electron withdrawing ability of the substituents and has been observed in other series of closo ‐boranes [12b, 14d, 26] …”

Metal‐Free Oxidative B−N Coupling of nido‐Carborane with N‐Heterocycles

“…2-tetrahydrofuryl and 1,4-dioxan-2-yl substituents at the 2-quinolyl position were also tolerated, affording two conformational isomers in 80 and 83 % combined yields,r espectively.E ither changing the substituents at the cage-carbon site or replacing the quinolyl with pyridyl moiety afforded comparable outcomes (7i-k). The compounds 7a-k were fully characterized by 1 H, 13 C, and 11 BNMR spectroscopy and HRMS.The molecular structures of 7c, 7g (7g-1 and 7g-2), and 7-k were unambiguously identified by single-crystal X-ray analysis (see Table S2).…”

“…[10] One major challenge is that the negatively charged cluster (7,8-C 2 B 9 H 12 À )p recludes the B À Hb ond from undergoing nucleophilic substitution. [11] So we envision that the nucleophilic attack toward the BÀHbond of a nidocarborane cage could be achieved if the electric charge could be made neutral after single-electron oxidation, thus furnishing an oxidative B À Hs ubstitution process.I ti sn oteworthy that the irreversible oxidation nature of nido-carborane cage has already been observed in electrochemistry with the oxidation potential of + 0.3-+ 0.4 Vv s. Fc/Fc + , [12] but this phenomenon is scarcely employed in synthetic chemistry. [11] So we envision that the nucleophilic attack toward the BÀHbond of a nidocarborane cage could be achieved if the electric charge could be made neutral after single-electron oxidation, thus furnishing an oxidative B À Hs ubstitution process.I ti sn oteworthy that the irreversible oxidation nature of nido-carborane cage has already been observed in electrochemistry with the oxidation potential of + 0.3-+ 0.4 Vv s. Fc/Fc + , [12] but this phenomenon is scarcely employed in synthetic chemistry.…”

Synthesis of Derivatives of closo-Dodecaborate Anion Based on Amino Acid Esters

“…Iodonium derivatives can enter into substitution reactions of PhI groups with a number of nucleophiles (pyridines, thioureas, cyanide ion, azide ion, etc.) [31][32][33][34][35]. In [36,37], the possibility of using phenyliodonium derivatives of the closo-dodecaborate anion and substituted analogs for the targeted introduction of various functional groups into the cluster was shown.…”