Coordinated and Clathrated Guests in the ${_{\infty }^{3}}$[Hg₆As₄]⁴⁺ Bicompartmental Framework: Synthesis, Crystal and Electronic Structure, and Properties of the Novel Supramolecular Complexes [Hg₆As₄](CrBr₆)Br and [Hg₆As₄](FeBr₆)Hg_0.6

Abstract

Two new supramolecular complexes [Hg(6)As(4)](CrBr(6))Br (1) and [Hg(6)As(4)](FeBr(6))Hg(0.6) (2) have been prepared by the standard ampoule technique and their crystal structures determined. Both crystallize in the cubic space group Pa$\bar 3$ with the unit cell parameter a=12.275(1) (1) and 12.332(1) A (2), and Z=4. Their structures consist of bicompartmental, three-dimensional [Hg(6)As(4)](4+) frameworks with cavities of two different sizes occupied by guest anions of different type. The bigger cavities are filled with the octahedral MBr(6) (n-) ions (M=Cr or Fe; n=3 or 4), whereas the smaller cavities trap either Br- ions (1) or Hg(0) (2). The analysis of the host-guest contacts has allowed a classification of the octahedral guests as coordinated and the monatomic guests as clathrated. Magnetic measurements and ESR spectroscopy data have given information about the interaction between the host and guests. Band structure calculations (HF and hybrid DFT level) indicate that both 1 and 2 are non-metallic, with a band gap of approximately 1.5 eV (B3LYP), and that the interaction between the host and guests is of predominantly electrostatic character. It is shown that though the electrostatic host-guest interaction is weak it plays an important role in assembling the perfectly ordered supramolecular architectures.

The Synthesis, Crystal and Band Structures, and Properties of the Quaternary Supramolecular Complexes [Hg6Z4](MX6)Hgy (Z = As, Sb; M = Hg, Cd; X = Cl, Br, I; y = 0, 0.5, 0.6)

“…The octahedral guest anions (CdCl 6 ) 4– , (HgCl 6 ) 4– , and (CdI 6 ) 4– are embedded in the larger cavities of the host framework in 1 , 2 , and 4 , respectively, whereas the smaller cavities trap the excess mercury atoms with 50 %, 50 %, and 60 % site occupancy for 1 , 2 , and 4 , respectively (Figure 2). Partial occupancy of the smaller cavities by mercury atoms has been reported previously in the literature, particularly for (Hg 6 As 4 )(HgCl 6 )Hg 0.4 , which is nearly same as 2 except for the different occupancy of the discrete mercury atom 2b,3b. Like the ternary compounds (Hg 6 P 4 )(HgBr 6 )3b and (Hg 6 Sb 4 )(HgBr 6 ),6a in which the larger cavities of the host framework are filled with the octahedral guest anions (HgX 6 ) 4– with the smaller cavities remaining empty, compound 3 is the first quaternary compound with this structural feature in metal pnictide halides (see Figure S1 in the Supporting Information).…”

“…The second one is the topology with the formula (Hg 6 Z 4 ) 4+ (Z = P, As, Sb),3,5 among which the frameworks possess cavities of two different sizes in close proximity. These are capable of trapping guests of two different types: octahedral guests with the formula (MX 6 ) 4– or (M′X 6 ) 3– (M = divalent metal atoms; M′ = trivalent metal atoms; X = Cl, Br,I)2b,2c,3 in the bigger cavities and monoatomic guests in the smaller ones. In most cases, the coordination centers of the octahedral guests are trivalent metal atoms rather than divalent metal atoms.…”

“…In most cases, the coordination centers of the octahedral guests are trivalent metal atoms rather than divalent metal atoms. Until now, two divalent metals, namely Hg3b,6 and Fe,2b acting as the coordination centers of the octahedral guest anions have been reported, among which only one quaternary supramolecular mercury pnictide halide, (Hg 4 As 6 )(FeBr 6 )Hg 0.6 ,2b has been characterized.…”

Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]

“…To balance the 4+ charge of the [Hg 6 As 4 ] moiety, the other cavity is filled by a lone halogen anion. Less common is the example of [Hg 6 As 4 ][FeBr 6 ]Hg 0.6 [33], in which the Fe atom has an oxidation state of +2, so the charges of the cation and anion are already balanced. The second cavity is partially filled by zerovalent mercury atoms.…”

Synthesis, crystal and band structures, and optical properties of a new framework mercury pnictides: [Hg4As2](InBr3.5As0.5) with tridymite topology

“…However, the known classes of microporous materials are overwhelmingly dominated by oxide, mixed oxide/fluoride matrices, sulfides, or halides [11][12][13][14][15][16][17]. Recently, mercury pnictides are well attractive because of their abundant structural features and distinctive electronic properties [18][19][20][21][22][23]. For instance, the propensity of mercury to linear two-coordination or to tetrahedral coordination can be exploited in the design of open-framework inorganic solids.…”