Regulated Adaptive Self-Assembly of Cu₃I₃ Supramolecular Clusters and their Photocatalytic Properties

Abstract

The regulated self-assembly of adjustable-structure cuprous iodide cluster-based supramolecules still presents a significant challenge. In this study, we adopt two flexible quinoline-based ligands (L 1 and L 2 ), which can form a C 3-symmetric cavity through conformation vibration. By the employment of a conformation-adaptive self-assembly strategy, a high yield of two host–guest-encapsulated cuprous iodide cluster-based supramolecular architectures [(Cu3I3)L 1–2 ] (C1 and C2) is precisely synthesized. The trapped Cu3I3 cyclic core is supported by organic ligands via Cu–N and Cu–O synergistic coordination bonds, associated with metal–metal bonding interactions. These neutral supramolecular clusters, C1 and C2, exhibit red emissions in the solid state and blue emissions in the solution. Additionally, such trinuclear clusters demonstrate high photocatalytic activity with azide–alkyne cycloaddition reactions in water.

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

“…The average separation of Cu I ···Cu I bonding motifs reached 2.71 Å, which was within the reasonable distance range of “cuprophilic” closed-shell interactions , (van der Waals radius of copper is 2.80 Å). As depicted in Figure c and Table S2, Cu1 connected with Cu2, Cu3, and Cu4 through strong metal–metal bonding interactions with a shorter separation of 2.762(6), 2.533(8), and 2.543(7) Å, respectively, in the [(Cu 5 I 8 ) 3– ]-type zigzag chain backbone. − Three four-coordinated copper atoms (Cu2, Cu3, and Cu4) formed a triangle motif multiply bridged by six bridging iodides (I2–I7). The terminal three-coordinated Cu5 was supported by three iodides (μ 3 -I6, μ 2 -I7, and I8), and the separation between Cu4 and Cu5 reached 3.067 Å.…”

“…Cuprous iodide salt and Cu­(II)/(I)-containing complexes have a potential application in Cu-catalyzed azide–alkyne cycloaddition reactions (CuAAC). − In comparison with various CuI-based catalyst systems, the polynuclear cuprous iodide cluster with high activity in water has been rarely reported. , For the anionic cluster C1 , all active cluster cores (Cu 5 I 8 ) were stabilized by the cationic triazine ligand, suggesting that this supramolecular cluster displayed potential catalytic activity for CuAAC reaction. To optimize the catalytic conditions for the CuAAC reaction, some interrelated control experiments were carried out, including solvent, catalyst species, and temperature.…”

“…In this case, the photocatalytic mechanism became too complicated to further understand. In comparison with neutral [Cu 3 I 3 ]-type cluster catalysts, , anionic cuprous iodide cluster C1 has more metal active sites ([Cu 5 I 8 ] 3– ), which can be completely exposed without a strong host–guest encapsulation and coordination interaction from outside organic ligands. However, the separated cluster active sites still exhibited high catalytic activity for the CuAAC reaction at 80 °C.…”

“…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.…”

“…By employing multiple-component conformational adaption and host–guest encapsulation self-assembly strategies, a family of cuprous iodide cluster-based assemblies including neutral supramolecular clusters [(Cu 3 I 3 )­L], dimeric cluster [Cu 8 I 8 ], and polyhedron cages [Cu 12 I 12 ], extended [Cu 4 I 4 ]-based and [Cu 6 I 5 ]-based coordination polymers were controlling self-assembled through “one-pot” reaction. Interestingly, these cuprous iodide cluster-based supramolecular catalysts showed excellent photocatalytic performance for CuAAC reaction in aqueous solution. − Among these cuprous iodide complexes, polynuclear supramolecular clusters have more catalytic sites and exhibit highly catalytic activity toward a common organic reaction. − …”