Self-assembled Structure of Inorganic–Organic Hybrid Crystals Based on Keggin Polyoxometallates [SMo₁₂O₄₀^2–] and Supramolecular Cations

Abstract

To investigate the network structure of inorganic−organic hybrid crystals, we synthesized a series of assemblies based on polyoxometallates (POMs) [SMo 12 O 40 2− ] and different supramolecular cations consisting of anilinium and crown ether derivatives. The compounds [(m-XAni + )(B-[18]crown-6)] 2 [SMo 12 O 40 2− ] (Ani + = anilinium; B[18]crown-6 = benzo[18]crown-6; X = F (1), Cl (2), Br (3), or I (4)), [and [(3-F-4-MeAni + ) 2 (DB[30]crown-10)][SMo 12 O 40 2− ]•2CH 3 CN (8) (4-MeAni + = 4-methylanilinium; DB[18]crown-6 = dibenzo[18]crown-6; 3-F-4-MeAni + = 3-fluoro-4-methylanilinium; DB[30]crown-10 = dibenzo[30]crown-10) were synthesized. Their crystal architectures were characterized according to the size and charge of the supramolecular cations. In 1−4, two adjacent supramolecular cations ([(m-XAni + )(B[18]crown-6)]) were connected through π•••π interactions forming sandwichtype dimers with the cations that were stacked in an antiparallel manner. In 8, DB[30]crown-10 included two cations constructing a larger divalent supramolecular cation [(3-F-4-MeAni + ) 2 (DB[30]crown-10)]. In 1−4 and 8, the ratio between [SMo 12 O 40 2− ] and the supramolecular cations was 1:1, and the latter formed rectangular-assembled structures. In 5, the π•••π stacking interaction was present in the adjacent B[18]crown-6. Monovalent supramolecular cations were present in 5−7 with a ratio of 1:2 between [SMo 12 O 40 2−] and the supramolecular cations. The supramolecular cations formed hexagonal-assembled structures.

Two Supramolecular Inorganic–Organic Hybrid Crystals Based on Keggin Polyoxometalates and Crown Ethers

“…The supramolecular cations are connected through the N-H···O hydrogen bonding interactions between the six oxygen atoms of the [18]crown-6 molecules and the nitrogen atoms of (3-F-4-MeAnis) cations. The average hydrogen bonding N-O distance is 2.9274 and 2.9137 Å for Supramolecular Cations 1 and 2, respectively, as shown in Table 2, which is similar to the standard N-H···O hydrogen bonding length of 2.91 Å [34], indicating that there exists a strong hydrogen bonding interaction between (3-F-4-MeAnis) cations and the [18] [20], which has a supramolecular dimer constructed by a crown ether and anilinium derivatives. Two nitrogen atoms (N1 and N2) are each included in the large cavity of [18]crown-6 molecules and located near its center.…”

“…Moreover, the charge of POMs can be modified by a chemical method to change the electrostatic interactions with an organic cation, resulting in the desired molecular assembled structures [19]. In addition, POMs with a large diameter can form an extended void space for embedding large organic cations [20]. Many supramolecular inorganic-organic hybrids based on POMs have been designed due to the structural advantages of POMs.…”

Two New 1D Supramolecular Compounds Based on PbI2 for Efficient Iodine Capture

“…In recent years, supramolecular chemistry has developed rapidly. A large number of inorganic–organic hybrid crystals with novel structures have been reported, and researchers began to pay attention to the improvement of their practical application value [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Supramolecular materials combine the stability of inorganic materials and the adjustability of organic materials, which gives organic–inorganic hybrid materials unique advantages in the field of iodine molecular enrichment [ 12 ].…”