Cu²⁺‐Mediated Dehydrogenative Coupling and Hydroxylation of an N‐Heterocyclic Ligand: From Generation of a New Tetratopic Ligand to the Designed Assembly of Three‐Dimensional Copper(I) Coordination Polymers

Abstract

Great interest has been focused on the rapidly expanding field of crystal engineering of two-(2D) and three-dimensional (3D) coordination polymers due to their structural and topological diversity as well as their potential application as functional materials.[1] The main strategy popularly used in this area is a building-block approach, [2] and much effort has been made towards the connection of suitable, predetermined building blocks into networks in order to obtain the desired materials. In this regard, the development of new multitopic building blocks is one of the central tasks. Recently, we have been investigating a few in situ metal/organic reactions such as ligand oxidative coupling, hydrolysis, and substitution by hydrothermal methods, [3] which provide an intriguing pathway for generating new, functional building blocks and coordination polymers. In particular, we have isolated and structurally characterized covalent hydrates of N-heterocyclic ligands in delocalized mixed-valence Cu I -Cu II complexes, which are not only an important bridge between coordination chemistry and organic heterocyclic chemistry, but can also be successfully applied to the assembly of functional molecular solids.[ ) (4; chtpy = a,a-1,4-dihydroxy-e,e,e,e-1,2,4,5-tetra(4-pyridyl)cyclohexane). This is the first time that simultaneous dehydrogenative coupling and hydroxylation of an N-heterocyclic ligand has been observed to generate a new, potentially tetratopic, coplanar ligand in situ.Pale-yellow or reddish crystals of 1-4 (ca. 18-35 % yield) were obtained from the in situ hydrothermal treatment of Cu(OH) 2 (freshly synthesized from Cu(NO 3 ) 2 ·3 H 2 O and NaOH) with 1,3-bis(4-pyridyl)propane (bpp), 1,4-cyclohexanedicarboxylic acid, and water in dilute HCl at 175-190 8C [Equation (1)]. The component diversification of the resulting Cu I -chtpy nets can be controlled simply by tuning the molar ratio of the starting materials. Elemental analysis and PXRD ( Figure S1 in the Supporting Information) confirmed the phase purity of the bulk materials. Compounds 1-4 are airstable and insoluble in water and most organic solvents.One of the most intriguing features regarding the synthesis is the direct observation of dehydrogenative coupling and hydroxylation of 1,3-bis(4-pyridyl)propane mediated by Cu 2+

Coordinative versatility of 3,5-bis(4-pyridyl)-1,2,4-triazole in the construction of monomeric copper(II) and polymeric copper(I) complexes

“…Furthermore, coordination polymers constructed from polynuclear clusters should be more stable and tend to exhibit multinary nets in consideration of the connectivity of different ligands [7]. The synthesis of these coordination polymers is highly influenced by a few factors such as the coordination preferences of the metal, the structural characteristics of the organic ligand, the metal-ligand ratio, the solvent and the reaction conditions [8][9][10].…”

Synthesis, Characterization and Quantum Chemical Studies on a Novel Cobalt(II) 1,2,3,4-Tetra-(4-pyridyl)-thiophene Coordination Polymer

“…9 Some tetratopic pyridyl-bridging ligands are of the recent surge of research interest, for example, 1,4-dihydroxy-1,2,4,5-tetra-(4-pyridyl)-cyclohexane, 1,2,4,5-tetra-(4-pyridyl)-benzene and 1,2,3,4-tetra-(4-pyridyl)-cyclobutane. [10][11][12][13][14] Compared with the linear 4,4´-bipyridine and 4,4´-bipyridine-like N,N´-donor ligands, 15 these tetradentate ligands induce unique structural topologies and exhibit interesting physical properties in many complexes. [10][11][12][13][14] In this field, however, the rigid symmetric ligand 1,2,3,4-tetra-(4-pyridyl)-thiophene (TPT, Scheme 1) is less explored in the self-assembly of coordination polymers.…”

Hydrothermal synthesis and crystal structure of a new coordination polymer: [Zn1(deta)(btec)(H2O)2]n

“…The use of multidentate organic ligands and metal ions to construct metal-organic frameworks (MOFs) has attracted much attention 6 due to their fascinating molecular and/or supramolecular structural diversity 7 and enormous potential applications as new functional material in gas storage and separation, magnetic materials, ion-exchange [8][9][10][11][12][13][14] , catalysis 15 , etc. The rigid aromatic polycarboxylate ligands, such as 1,4-benzenedicarboxylate (1,4-bdc) 16-17 , 1,3-benzenedicarboxylate (m-bdc) [18][19] , 1,2-benzenedicarboxylate (1,2-bdc) [20][21] , 1,3,5-benzenetricarboxylate (1,3,5-btc) [22][23] , have been widely used as bridging ligands for the design and synthesis of porous materials with robust structures and high porosity.…”