Charge‐Assisted Halogen Bonding in an Ionic Cavity of a Coordination Cage Based on a Copper(I) Iodide Cluster

Abstract

The design of molecular containers capable of selectively binding specific guest molecules presents an interesting synthetic challenge in supramolecular chemistry. Here, we report the synthesis and structure of a coordination cage assembled from Cu 3 I 4 À clusters and tripodal cationic N-donor ligands. Owing to the localized permanent charges in the ligand core the cage binds iodide anions in specific regions within the cage through ionic interactions. This allows the selective binding of bromomethanes as secondary guest species within the cage promoted by halogen bonding, which was confirmed by single-crystal X-ray diffraction.

Self-Assembly of an Anionic [Cu5I8]3– Supramolecular Cluster Driven by Ion-Pair Interaction and Catalytic Properties

“…In addition, the formation of solvated C1 with the molecular formula of [(Cu 5 I 8 ) 3– ]­( L 1 ) 3+ was further demonstrated by ESI-MS in the methanol/dimethyl sulfoxide solution, which is depicted in Figure S8. The relative mass-to-charge ratio ( m / z ) peaks at 1348.88, 1506.37, 1593.43, and 1741.48 correspond to the solvated molecular fragments of [ L 1 + Cu 3 I 3 + OH ̅ + Br ̅ + CH 3 OH] + , [ L 1 + Cu 4 I 4 + OH ̅ + Br ̅ ] + , [ L 1 + Cu 4 I 4 + 2OH ̅ + 2CH 3 CH 2 OCH 2 CH 3 ] + , and [ L 1 + Cu 5 I 5 + 2OH ̅ + CH 3 OH + CH 3 CH 2 OCH 2 CH 3 ] + cationic molecular peaks, respectively, which were consistent with the theoretical results. − Conclusively, these analysis results indicated that the [(Cu 5 I 8 ) 3– ]-type anionic cluster C1 partially dissembled into cluster fragments in solution, verified by SCXRD (Figures S7 and S8). The cuprous iodide cluster C1 was also identified by X-ray photoelectronic spectrum (XPS) measurements, and the characteristic peaks of Cu 2p were found at 932.15 and 952.0 eV, suggesting that the oxidation state of the copper center was +1 in the anionic cluster (Figure S12).…”

“…The UV–vis absorption spectrum of cuprous iodide supramolecular cluster C1 was measured in the solid state and solution. As presented in Table S3 and Figures S15–S20, cluster C1 exhibited a broad absorption band ranging from 235 to 320 nm and a weak peak was found at 420 nm in the solid-state electron absorption spectrum, which were tentatively assigned to the n–π* mixed with π–π* electronic transitions in an organic ligand (ILCT) and metal-to-ligand charge transfer (MLCT), respectively. − In the acetonitrile solution of cluster C1 ( c = 1 × 10 –5 mol L –1 , 298 K), an intense absorption band appeared at 286 nm (ε = 24 590 M –1 cm –1 ) and a lower energy band can be observed at 369 nm (ε = 2820 M –1 cm –1 ). Based on previously reported cuprous iodide complexes, − in comparison with free organic ligand L 1 , these electron absorption bands possibly originated from the mixed ILCT with MLCT. − ,− …”

“…High-nuclearity coordination clusters have attracted extensive attention because of their structural diversity − and wide-ranged application prospects in the field of photoelectron devices, − electrical conductivity, metal–organic catalysis, and fluorescent sensing. − As a common aggregate of copper­(I) atoms coordinated with halide anions, cuprous iodide clusters exhibited a variety of molecular arrays with rich electronic structures, including neutral, cationic, and anionic [Cu x I y ] x − y coordination moieties. − In the neutral cuprous iodide cluster aggregates [CuI] x , uncharged organic/inorganic ligands can support and stabilize the [CuI] x cores via Cu–N, Cu–S, or Cu–P coordination interactions, − such as Cu 2 I 2 rhomboid dimers, − Cu 3 I 3 trimers, Cu 4 I 4 cubane tetramers, , Cu 6 I 6 staircase hexamers, − Cu 7 I 7 pinwheel heptamers, − Cu 8 I 8 staircase octamers, and so forth. In order to construct ionic cuprous iodide clusters with high nuclearity, some cationic heteroleptic ligands were developed and reacted with copper iodide salt. − Up to date, it has rarely been reported for anionic cuprous iodide clusters, such as [Cu 4 I 6 (TPP) 2 ]­(TPP = alkyl-tris­(2-pyridyl)­phosphonium halides), [Cu 6 I 7 ] − , [L 4 (Cu 3 I 4 ) 4 ] 8+ , and so on . Among these ionic cuprous iodide cluster systems, the [Cu x I y ] x − y coordination moieties with a highly nuclear nature were self-assembled as driven by the intramolecular electrostatic interaction from anion–cation pairs in the aggregation process. , However, the structural diversity is influenced by multiple factors, which increase the difficulty in the controlling synthesis of ionic cuprous iodide clusters. ,,− …”

“…In order to construct ionic cuprous iodide clusters with high nuclearity, some cationic heteroleptic ligands were developed and reacted with copper iodide salt. − Up to date, it has rarely been reported for anionic cuprous iodide clusters, such as [Cu 4 I 6 (TPP) 2 ]­(TPP = alkyl-tris­(2-pyridyl)­phosphonium halides), [Cu 6 I 7 ] − , [L 4 (Cu 3 I 4 ) 4 ] 8+ , and so on . Among these ionic cuprous iodide cluster systems, the [Cu x I y ] x − y coordination moieties with a highly nuclear nature were self-assembled as driven by the intramolecular electrostatic interaction from anion–cation pairs in the aggregation process. , However, the structural diversity is influenced by multiple factors, which increase the difficulty in the controlling synthesis of ionic cuprous iodide clusters. ,,− (i) The mutable geometric configuration of Cu­(I) centers and complicated Cu–I coordination manners will significantly increase the uncertainty in structure prediction and controllable preparation. (ii) The self-aggregation behavior of [CuI] x cluster was a random and spontaneous process that can be easily influenced by some factors, such as reaction conditions and temperature.…”

Halogen bond and polymorphism in trans-bis(2-iodo-5-halopyridine)dihalocopper(ii) complexes: crystallographic, theoretical and magnetic studies

“…In the latter, the halogen bond acceptor has to be negatively charged, and hence it is known as charge-assisted halogen bond. 12,[24][25][26] These interactions may be represented as C-Y⋯X-M where M = metal cation. These halogen bonding interactions are known as halogen⋯halogen contacts, where both halogen bond donor and acceptor are halogen atoms.…”