1-Pyridine- and 1-Quinuclidine-1-boraadamantane as Models for Derivatives of 1-Borabicyclo[2.2.2]octane. Experimental and Theoretical Evaluation of the B−N Fragment as a Polar Isosteric Substitution for the C−C Group in Liquid Crystal Compounds

2-Alkylphosphino-1-boraadamantanes

Boraadamantanes are a privileged class of caged group 13 compounds having a trigonal pyramidal (non-VSEPR) ground-state. The Lewis acid-base chemistry of this type of compound is underdeveloped when compared to acyclic derivatives. This report provides the first examples of bifunctional boraadamantanes with an appended phosphine moiety (also the first boraadamantanes having a phosphorus-boron bond). Using this scaffold, boraadamantane coordination compounds are accessed for the first time.

The Field of Main Group Lewis Acids and Lewis Superacids: Important Basics and Recent Developments

New developments in the field of Lewis acidity are highlighted, with the focus of novel Lewis acids and Lewis superacids of group 2, 13, 14, and 15 elements. Several important basics, illustrated by modern examples (classification of Donor-Acceptor (DA) complexes, amphoteric nature of any compound in terms of DA interactions, reorganization energies of main group Lewis acids and the role of the energies of frontier orbitals) are presented and discussed. It is emphasized that the Lewis acidity phenomena are general and play vital role in different areas of chemistry: from weak "atomophilic" interactions to the complexes of Lewis superacids.

Unsupported Donor-Acceptor Complexes of Noble Gases with Group 13 Elements

Unsupported donor-acceptor complexes of noble gases (Ng) with group 13 elements have been theoretically studied using density functional theory. Calculations reveal that heavier noble gases form thermodynamically stable compounds. The present study reveals that no rigid framework is necessary to stabilize the donor-acceptor complexes. Rather, prepyramidalization at the Lewis acid center may be an interesting alternative to stabilize these complexes. Detailed bonding analyses reveal the formation of two-center-two-electron dative bonding, where Ng atoms act as a donor.

Investigation of the Lewis acidic behaviour of an oxygen-bridged planarized triphenylborane toward amines and the properties of their Lewis acid–base adducts

Lewis acid behavior of an oxygen-bridged triphenylborane (1) to amines and the properties of Lewis acid–base adducts of 1 with amines have been investigated.

Strategies toward realization of unsupported transition metal-boron donor-acceptor complexes: an insight from theory

Pre-pyramidalization of the boron centre in the Lewis acidic groups is a prerequisite for the formation of unsupported donor-acceptor complexes with Lewis basic metal fragments such as [Pt(NHC)2].

Quaternary salts derived from 3-substituted quinuclidine as potential antioxidative and antimicrobial agents

Two series of novel ammonium salts containing the quinuclidine moiety were prepared in order to evaluate their antioxidative, antibacterial and antifungal potential. The synthesized homologues of 3-hydroxy (QOH) and 3-chloroquinuclidine (QCl) with the different N-benzyl substituents at the para-position (bromo, chloro or nitro group) were obtained in very good yields and characterized by IR and NMR spectroscopies and elemental analysis. All compounds were tested for antioxidative activity using the oxygen radical absorbance capacity (ORAC) assay and among tested samples, N-p-nitrobenzyl-3-hydroxyquinuclidinium bromide (QOH-4) exhibited the highest antioxidative potential (293.80 nmol (TE) mL-1), which was further investigated by the DNA nicking assay. The biological activity of selected compounds was evaluated by measuring the zone of inhibition and by determining the minimal inhibitory concentration (MIC) against three Gram-positive bacteria (B. cereus, E. faecalis and S. aureus), three Gram-negative bacteria (E. coli, P. aeruginosa and C. sakazakii) and three fungi species (C. albicans, A. niger and P. notatum). The bioactivity assay showed that some newly synthetized quaternary quinuclidinium compounds display a comparable or even better antibacterial and antifungal activity than the reference drugs such as gentamicin (GEN), cefotaxime (CTX) and amphotericin B (AMPHB). Among the tested compounds, N-p-chlorobenzyl-3-hydroxyquinuclidinium bromide (QOH-3) exhibited a considerable antibacterial efficiency against P. aeruginosa (MIC=0.39 µg mL-1) and QOH-4 displayed a potent antifungal activity against C. albicans (MIC=1.56 µg mL-1).