Homochiral Metal–Organic Frameworks Embedding Helicity Based on a Semirigid Alanine Derivative

Abstract

Five novel homochiral metal−organic frameworks (HMOFs) have been synthesized using a semirigid alanine-derived ligand and varied auxiliary N-donor ligands, namely, [Cu 2 (TMAla) Eu,3; Tb,4; Gd,5), where H 2 TMAla = terephthaloyl-mono(L-alanine), bipy = 4,4′-bipyridine, bpea = 1,2bis(4-pyridyl)ethane, phen = 1,10-phenanthroline. Crystallographic analysis indicates that all the complexes contain homochiral left-and/or right-handed helical chains, which are constructed by TMAla fragments and metal ions. Meanwhile, the introduction of auxiliary N-donor ligands gives rise to the formation of HMOFs with different structural topologies. Complex 1 shows a three-dimensional (3D) quartzdual net with a 4-connected (7 5 •9) topology in the presence of bipy. Complex 2 possesses a novel 3D pillared-layer framework with a (3,4,4)-connected (6•10 4 • 12)(6 3 ) 2 (6 4 •10 2 ) topology by using bpea instead of bipy. Complexes 3−5 are isomorphous and feature a 2-fold interpenetrating 3D quartz net with a 4-connected (6 4 •8 2 ) topology due to the participation of phen. Complexes 3 and 4 exhibit characteristic Eu(III) and Tb(III) emissions in the red and green light regions, respectively. The solid-state circular dichroism (CD) spectra of all complexes exhibit strong CD signals. Our results highlight that the semirigid chiral linker is successful for the construction of interesting HMOFs with unique helical chains.

Homochiral Porous Metal–Organic Frameworks Constructed from a V-Shaped Alanine Derivative Based on Pyridyl-Dicarboxylate

“…It is a usual synthesized approach for amino acid derivatives that the polycarboxylates as substitutional groups modify the amino groups of natural amino acids. Currently, linear, − V-shaped, ,, and triangular − amino acid derivatives have been researched for the fabrication of multifunctional HPMOFs. However, few HPMOFs incorporating permanent porosity and intriguing structures are reported. − Using the pyridyl-carboxylate unit instead of the common polycarboxylate group to decorate the natural amino acid has rarely been investigated. − Therefore, the application of pyridyl-carboxylate-amino acid derivatives for the construction of stable HPMOFs remains an unexplored field and affords great potential owing to diverse coordination patterns and plentiful coordination points in comparison to the usual polycarboxylate-amino acid derivatives.…”

Structural Analysis and Controllable Fabrication of Two Pentazolate-Based 3D Topological Networks

“…Another prominent structural feature of the MPF-4 framework is the double helical chains that makes up channels. Helicity is a special form of one-dimensional chirality, − and MPF-4 possesses two interpenetrating left-handed topology chains simultaneously (Figure e,f). In general, the MOF homochirality is transmitted from the building units to the whole framework, while the fabrication of MPF-4 is introduced from achiral cyclo -N 5 – anion precursors based on auxiliary MSM ligands.…”

Chiral Cd(II) Coordination Polymers Based on Amino Acid Derivatives: The Effect of Side Chain on Structure

“…The structural flexibility of α-amino acids, which may hinder the formation of robust porous frameworks, can be reduced by functionalization with suitable rigid aromatic units. − A straightforward implementation of this strategy involves appending a benzoate group to the N -terminus of the amino acid, which can be achieved in two synthetic steps to obtain semirigid terephthaloyl mono amino acid linkers (H 2 TMXxx, Xxx = amino acid). Five homochiral frameworks, some of which contain significant pore space (up to 2968 Å 3 per unit cell or 36.2% of the crystal volume), have been constructed using the alanine-derived ligand (H 2 TMAla), demonstrating the propensity of H 2 TMXxx linkers to promote the formation of porous homochiral coordination polymers. The inclusion of rigid N-donor coligands was used to further increase the dimensionality and porosity of the frameworks.…”

“…A reliable and inexpensive strategy for preparing homochiral coordination polymers is to use ligands derived from commercially available chiral molecules. − The naturally occurring α-amino acids are promising candidates for chiral precursors as they are nontoxic, inexpensive and can be readily obtained in high enantiopurity . The structural flexibility of α-amino acids, which may hinder the formation of robust porous frameworks, can be reduced by functionalization with suitable rigid aromatic units. − A straightforward implementation of this strategy involves appending a benzoate group to the N -terminus of the amino acid, which can be achieved in two synthetic steps to obtain semirigid terephthaloyl mono amino acid linkers (H 2 TMXxx, Xxx = amino acid). Five homochiral frameworks, some of which contain significant pore space (up to 2968 Å 3 per unit cell or 36.2% of the crystal volume), have been constructed using the alanine-derived ligand (H 2 TMAla), demonstrating the propensity of H 2 TMXxx linkers to promote the formation of porous homochiral coordination polymers.…”