Carboxylato Bridged Cyclic SBUs as Robust Features in a Series of Cu(II) Coordination Polymers and Halogen···Halogen Interactions in Crystal Packing

Abstract

Four new pyridine/meta-substituted halopyridine appended coordination polymers (CPs) {[Cu(ip) 6 (py and [Cu(ip) 2 (3-Ipy) 2 ] n (4) (py = pyridine, 3-Clpy = 3chloropyridine, 3-Brpy = 3-bromopyridine, 3-Ipy = 3-iodopyridine, and H 2 ip = isophthalic acid) have been synthesized by a diffusion method. The compounds are structurally characterized by the single crystal X-ray diffraction technique, and supramolecular interactions are studied by geometrical and density functional theory calculations. The study reveals that the compounds 1−3 form a two-dimensional (2D) coordination polymeric structure with carboxylato bridged dimeric Cu(II) cyclic secondary building units. However, a cyclic supramolecular synthon involving four halogen (X = Cl, Br) atoms has been observed in 2 and 3. This cyclic halogen synthon combined with a pyridine ring forms a (π•••π)+X•••X+(π•••π) mega-synthon, which dictates the dimensionality of 2D CPs into a three-dimensional (3D) network. However, compound 4 with a larger I atom does not show such interactions and forms a 1D tape structure.

Halogen···Halogen and π–Hole Interactions in Supramolecular Aggregates and Electrical Conductivity Properties of Cu(II)-Based 1D Coordination Polymers

“…Keeping this in mind, we have synthesized the two new one-dimensional (1D) CPs [Cu­(5-nip)­(3-Clpy) 2 ] n ( 1 ) and [Cu­(5-nip)­(3-Brpy) 2 ] n ( 2 ) using a 5-nitroisophthalic acid (H 2 5-nip) and 3-chloropyridine (3-Clpy)/3-bromopyridine (3-Brpy) mixed-ligand system (Scheme ). Herein, the introduction of a nitro group leads to steric hindrance, which prevents further bridging of 5-nip ligands into a two-dimensional (2D) network as observed in our previous work . Moreover, the nitro group is involved in X···NO 2 π-hole interactions that are also relevant in determining the solid-state structures of compound 1 and 2 .…”

“…31−35 Recently, we have reported a series of Cu(II)-based CPs made up of isophthalate and meta-substituted halopyridine to investigate the effect of X•••X interactions in the crystal packing for the formation of the overall topology of the network. 36 In a continuation of this work, we intend to introduce a nitro group by replacing isophthalate with nitroisophthalate, keeping the auxiliary ligand the same, and to check whether any structural diversity coupled with varied applications may emerge. Keeping this in mind, we have synthesized the two new onedimensional (1D) CPs [Cu(5-nip)(3-Clpy) 2 ] n (1) and [Cu(5nip)(3-Brpy) 2 ] n (2) using a 5-nitroisophthalic acid (H 2 5-nip) and 3-chloropyridine (3-Clpy)/3-bromopyridine (3-Brpy) mixed-ligand system (Scheme 1).…”

“…Herein, the introduction of a nitro group leads to steric hindrance, which prevents further bridging of 5-nip ligands into a two-dimensional (2D) network as observed in our previous work. 36 Moreover, the nitro group is involved in X•••NO 2 π-hole interactions that are also relevant in determining the solid-state structures of compound 1 and 2. These interactions have been investigated using density functional theory (DFT) and molecular electrostatic potential (MEP) surface calculations.…”

“…Recently, we have reported a series of Cu­(II)-based CPs made up of isophthalate and meta-substituted halopyridine to investigate the effect of X···X interactions in the crystal packing for the formation of the overall topology of the network . In a continuation of this work, we intend to introduce a nitro group by replacing isophthalate with nitroisophthalate, keeping the auxiliary ligand the same, and to check whether any structural diversity coupled with varied applications may emerge.…”

In Situ Trans–Cis Isomerization of Naphthylvinylpyridine Ligand in a Zinc(II) Coordination Polymer: Liquid and Vapor Phase Sensing of Mutagenic Pollutants and Nitroexplosives

“…In the era of functional materials, polymeric coordination compounds − offer remarkable contributions in the view of potential applicability, because of their structural assortment as well as the prevalent thermal and chemical constancy. These polymeric forms of coordination compounds are named as coordination polymers (CPs) , or coordination networks (CNs) , or metal–organic frameworks (MOFs) − depending upon their dimensionality, where the metal centers/clusters are connected through diverse organic ligands. In the preceding period, mixtures of organic ligands (O-donor and N-donor) were isotypically utilized to achieve structural diversity and desired properties.…”