Macrocycles and Coordination Polymers Derived from Self-Complementary Tectons Based on N-Containing Boronic Acids

Abstract

A series of N-containing boronic esters have been prepared by combination of 3-pyridineboronic acid (3-pyba), 4-pyridineboronic acid (4-pyba), and 5-isoquinolineboronic acid (5-iqba) with ethanol, 1,2-ethanediol, and 1,3-propanediol. The resulting self-complementary tectons (SCTs) assembled further through N → B bond formation to give one tetranuclear macrocyclic and four one-dimensional polymeric boron complexes: [(3-py)B(OEt) 2 ] 4 (2), [(3-py)B(OCH 2 CH 2 O)] n (3), [(4-py)B(OEt) 2 ] n (4), [(5-iq)B(OCH 2 CH 2 O)] n (6), and [(5-iq)B(OCH 2 CH 2 CH 2 O)] n (7). In conjunction with the previously reported pentadecanuclear boroxine cage (1) and high-dimensional assemblies derived from pentaerythritol, [(4-py), it was shown that a single class of self-complementary boron-based tectons can give a varied series of finite and infinite supramolecular aggregates. A comparative structural characterization of boron complexes 2−4 and 6−7 by single-crystal X-ray diffraction analysis and quantum-chemical calculations revealed that the corresponding SCTs could have been organized in all cases in the form of tetrameric macrocycles, as it occurred for 2, indicating that intermolecular noncovalent interactions during crystallization probably play a significant role in the output of the assembly process and influence the formation of supramolecular isomers. This observation was supported by a comparison of the molecular geometries of a series of tetranuclear macrocyclic and related linear oligomeric boronic esters derived from 3-pyba, 4-pyba, and 5-iqba, whose structures have been optimized by quantum-chemical calculations at the (B3LYP/cc-pVDZ) level of theory. The calculated structure of [(3-py)B(OEt) 2 ] 4 was in good agreement with the structure obtained experimentally by single-crystal X-ray diffraction analysis. For the cyclo-tetramers derived from 3-pyba and 5-iqba, all common conformers known from calixarene chemistry have been analyzed (cone, 1,3-alternate, 1,2-alternate, and partial cone), showing that the boronic ester group has a significant influence on their relative stability.

Supramolecular arrangement and photophysical properties of a dinuclear cyanophenylboronic acid ester

“…As observed previously for other related compounds (Cruz-Huerta et al, 2012, the six-membered aliphatic rings formed by atoms B1/O1/C1/C2/C3/O2 and B2/O3/C4/C2/C5/ O4 have half-chair conformations, with B-O-C-C torsion angles ranging from À25.4 (4) to 34.5 (4) . The B-C spiro -B angle is 137.8 (2) , similar to the values reported for similar spiro boronic acid esters (Day et al, 2007;Cruz-Huerta et al, 2012;Salazar-Mendoza et al, 2013;Tahara et al, 2014). The molecular structure of (I) reveals also that the cyanophenyl rings linked to the B atoms are not coplanar, having a centroid-C spiro -centroid angle of 131.5 .…”

“…Boronic acids undergo reactions with alcohols, particularly diols, to give boronic esters (Fujita et al, 2008). Of these, pentaerythritol forms stable dinuclear cyclic boronic esters when reacted with arylboronic acids in a 1:2 stoichiometric ratio, and this reaction constitutes an interesting strategy for the construction of diverse supramolecular compounds (Cruz-Huerta et al, 2012;Salazar-Mendoza et al, 2013). This is because three-coordinate boron species can act as Lewis acids toward a broad range of electron-rich substrates, in particular, amine and pyridine derivatives (Hö pfl, 1999), or exhibit conjugated -systems that are often strongly coloured and highly luminescent (Santos et al, 2016;Li et al, 2013).…”

Hierarchical supramolecules and organization using boronic acid building blocks

“…Their subsequent study found that replacing pentaerythritol with ethanol or simple diols led to the formation of one tetranuclear macrocyclic and four one-dimensional polymeric boronates. 35 Severin et al have investigated supramolecular polymerization based on the combination of boronate esterification and N-B dative bond formation. 36 Taking into account that the binding constants (K a ) between functional groups typically required to obtain polymers with significant molecular weights are equal to or more than 10 6 M À1 , the K a values of dioxaboles with pyridine were fully evaluated.…”

Boron Macrocycles Based on Multicomponent Assemblies using (3‐Aminophenyl)boronic Acid and Pentaerythritol as Common Reagents; Molecular Receptors toward Lewis Bases

“…Thus, the combination of boronate esters with amine derivative ligands is a very important strategy with which to construct macrocyclic and polymeric systems, wherein the utilization of dative B–N bonds significantly supports the formation of supramolecular moieties 7,26. Recently, the formation of macrocycles including 2D and 3D polymeric structures was reported to take place by self‐assembly of boronate esters using pentaerythritol and N ‐substituted arylboronic acids 27,28…”