Hofmann-type Clathrates Research Articles

Perspective from a Hubbard U-density corrected scheme towards a spin crossover-mediated change in gas affinity.

By employing a recently proposed Hubbard U density-corrected scheme within density functional theory, we provide design principles towards the design of materials exhibiting a spin crossover-assisted gas release. Small molecular fragments are used as case study to identify two main mechanisms behind the change in binding energy upon spin transitions. The feasibility of the proposed mechanism in porous crystals is assessed by correlating the change in binding energy of CO2, CO, N2, and H2, upon spin crossover, with the adiabatic energy difference associated with the spin state change of the square-planar metal in Hofmann-type clathrates (M = Fe, Mn, Ni). A few promising cases are identified for the adsorption of intermediate ligand field strength molecules such as N2 and H2. The latter stands out as the most original result as the strong interaction in low spin, as expected from a Kubas mechanism, results in a large change in binding energy. This work provides a general perspective towards the engineering of open-metal site frameworks exhibiting local environments designed to have a spin crossover upon adsorption of specific gas molecules.

Synthesis of Hofmann-type Zn(H2O)2Ni(CN)4.nG (G = water and 1,4-dioxane)clathrates and the determination of their structural properties by variousspectroscopic methods

Two new 2-dimensional cyanide-bridged coordination polymers [Zn(H$_{2}$O)$_{2}$Ni(CN)$_{4}$ 6(H$_{2}$O) and Zn(H$_{2}$O)$_{2}$ Ni(CN)$_{4}$ 3(C$_{4}$H$_{8}$O$_{2})$], which were similar to Hofmann-type clathrates, were synthesized based on [Ni(CN)$_{4}$]$^{2-}$ and Zn$^{2+}$ as building blocks. These substances were synthesized as compounds in crystalline form. Thes tructures of the crystalline compounds were characterized via their spectral analyses. General information about the structures of the newly obtained Hofmann-type clathrates was obtained from their vibration spectra by considering significant changes in the vibration peaks of the cyanide group, water ligand molecule, and guest molecules (water and 1,4-dioxane). The thermal behavior of the Hofmann-type clathrates was investigated in the range of 25-500 $^{\circ}$ C. In addition, experimental data on the magnetic properties of the Hofmann-type clathrates were obtained using the Gouy method under normal conditions. Information on the properties of the structures of the Hofmann clathrates was obtained by applying the single crystal diffraction technique. The asymmetric unit of the first Hofmann-type clathrate contained 1 Zn(II) ion, 1 Ni(II) ion, 1 cyanide ligand, 1 water ligand molecule, and 2 guest water molecules. The asymmetric unit of the second Hofmann-type clathrate contained 1 Zn(II) ion, 1 Ni(II) ion, 2 cyanide ligands, 1 water ligand molecule, and 2 half guest 1,4-dioxane molecules.

High-Pressure Effects on Hofmann-Type Clathrates: Promoted Release and Restricted Insertion of Guest Molecules

The search for effective methods to accurately control host-guest relationship is the central theme of host-guest chemistry. In this work, high pressure successfully promotes guest release in the Hofmann-type clathrate of [Ni(NH3)2Ni(CN)4]·2C6H6 (Ni-Bz) and restricts guest insertion into Ni(NH3)2Ni(CN)4 (Ni-Ni). Because of the weak host-guest interactions of Ni-Bz, external force gradually removes guest benzene from the host framework, leading to puckered layers. Further theoretical calculations reveal the positive pressure contribution to breaking the energy barrier between Ni-Bz and Ni-Ni, explaining guest release from an energy standpoint. Inversely, guest insertion is restricted in the synthesized host of Ni-Ni because of the steric hindrance effect at high pressure. This study not only reveals structural effects on host-guest behaviors but also proves the role of pressure in controlling host-guest interactions. This unique observation is also crucial for the further application of host-guest materials in sustained and intelligent drug release, molecular separation, and transportation.

Spin-Crossover Behavior of Hofmann-Type-Like Complex Fe(4,4’-bipyridine)Ni(CN)4·nH2O Depending on Guest Species

A newly prepared metal complex Fe(4,4’-bipyridine)Ni(CN)4·nH2O, which was estimated to have a structure similar to the Hofmann-type clathrate host, changed its color from orange to deep orange and yellow on exposure to ethanol and acetone vapor, respectively, and the respective samples showed thermally induced two-step and one-step spin transitions.

Molecular iodine adsorption within Hofmann-type structures M(L)[M'(CN)4] (M = Ni, Co; M' = Ni, Pd, Pt): impact of their composition.

A series of thermally stable Hofmann-type clathrate structures with the general formula M(pz)[M'(CN)4], where M and M' are bivalent metal ions M(II) = Ni(II), Co(II), M(II)' = Ni(II), Pd(II), Pt(II), and pz is the pyrazine bidentate ligand, was synthesized and investigated for the efficient entrapment of iodine (I2) in solution and in the gas phase. Iodine-containing clathrates thus prepared were analysed to determine the saturation capacity, thermal stability, guest-induced structural changes of the clathrate's lattice and the nature of the confined iodine according to the chemical composition of the host structure. An efficient confinement of about 1 I2 per unit cell is observed for the series of clathrates with the Ni(II) and Pd(II) ions in the square planar position whatever the bivalent metal ion in the octahedral position. Specific responses in the lattice adjustment are detected for Co(II) in the octahedral and Pd(II) in the square planar positions.

Iodine capture by Hofmann-Type clathrate Ni(II)(pz)[Ni(II)(CN)4

The thermally stable Hofmann-type clathrate framework Ni(II)(pz)[Ni(II)(CN)4] (pz = pyrazine) was investigated for the efficient and reversible sorption of iodine (I2) in the gaseous phase and in solution with a maximum adsorption capacity of 1 mol of I2 per 1 mol of Ni(II)(pz)[Ni(II)(CN)4] in solution.

FT-IR spectroscopic and thermal study of M(1,6-hexanedithiol)Ni(CN)4⋅2(1,4-dioxane) clathrate (M=Mn, Co, Ni and Cd)

Abstract In this study, clathrate of Cyclohexanethiol-tetracyanonickel-dioxane, given by the formula M(Cyclohexanethiol) 2 Ni(CN) 4 ·(l,4-dioxane) (M = Mn, Co, Ni and Cd), is obtained for the first time through chemical methods. The FTIR spectroscopic data in the region of (4000–400) cm −1 was recorded and the IR frequencies were given and explained in detail. The thermal behavior of these clathrates was also investigated by thermo-gravimetric analysis (TGA), differential thermal analysis (DTA) and derivative thermal gravimetric analysis (DTG). The spectral and thermal analysis results of the newly synthesized clathrate of Cyclohexanethiol–tetracyanonickel–dioxane suggest that these clathrates are new examples of the Hofmann-type clathrates. In our study, the Hofmann-type clathrates formed by bounding electrons of sulfur-donor atoms of the thiol group of Cyclohexanethiol ligand molecule to transition metal atoms consist of the corrugated |M–Ni(CN) 4 | ∞ polymeric layers which are held in parallel through the van der Walls interactions (–M–Cyclohexanethiol⋯Cyclohexanethiol–M–).

Synthesis and vibrational spectroscopic analysis of some Hofmann type clathrates

New Hofmann type clathrates in the form of M(pp) 2Ni(CN) 4·2G (where pp = 1-phenylpiperazine, G = 1,4-dioxane and M = Ni, Co or Cd) have been prepared in powder form and their FT-IR and FT-Raman spectra are reported. The results suggest that the present compounds are similar in structure to the Hofmann type clathrates and their structures consist of conjugated polymeric layers of |M–Ni(CN) 4| ∞ with the pp bound to the metal (M) atom.

FTIR spectroscopic and thermal study of M(Cyclohexanethiol) 2Ni(CN) 4·(1,4-dioxane) clathrate (M = Mn, Co, Ni and Cd)

In this study, clathrate of Cyclohexanethiol-tetracyanonickel-dioxane, given by the formula M(Cyclohexanethiol) 2Ni(CN) 4·(l,4-dioxane) (M = Mn, Co, Ni and Cd), is obtained for the first time through chemical methods. The FTIR spectroscopic data in the region of (4000–400) cm −1 was recorded and the IR frequencies were given and explained in detail. The thermal behavior of these clathrates was also investigated by thermo-gravimetric analysis (TGA), differential thermal analysis (DTA) and derivative thermal gravimetric analysis (DTG). The spectral and thermal analysis results of the newly synthesized clathrate of Cyclohexanethiol–tetracyanonickel–dioxane suggest that these clathrates are new examples of the Hofmann-type clathrates. In our study, the Hofmann-type clathrates formed by bounding electrons of sulfur-donor atoms of the thiol group of Cyclohexanethiol ligand molecule to transition metal atoms consist of the corrugated |M–Ni(CN) 4| ∞ polymeric layers which are held in parallel through the van der Walls interactions (–M–Cyclohexanethiol⋯Cyclohexanethiol–M–).

Vibrational spectroscopic study on some Hofmann type clathrates: M(2-(1-cyclohexenyl)ethylamine) 2Ni(CN) 4·2benzene (M = Ni and Cd)

New Hofmann type benzene clathrates in the form of M(CyHEA) 2Ni(CN) 4·2benzene (where CyHEA = 2-(1-cyclohexenyl)ethylamine and M = Ni or Cd) have been prepared in powder form and FT-IR and Raman spectra have been reported. The results suggest that title compounds are similar in structure to Hofmann type clathrates and their structures consist of polymeric layers of |M–Ni(CN) 4| ∞ with the CyHEA molecule bounded to the metal atoms (M).

<b>Vibrational spectroscopic investigation of some Hofmann type clathrates: M(4-phenylpyridine)<sub>2</sub>Ni(CN)<sub>4</sub>.2G (M = Ni, Co and Cd, G = 1,4-dioxane) </b>

New Hofmann type clathrates in the form of M(4-Phpy) 2 Ni(CN) 4 .2G (where 4-Phpy = 4-phenylpyridine, G = 1,4-dioxane and M = Ni, Co and Cd) have been prepared in powder form and their FT-IR and Raman spectra have been reported. The results suggest that these compounds are similar in structure to the Hofmann type clathrates and their structures consist of polymeric layers of |M-Ni(CN) 4 | ∞ with the 4-Phpy bound to the metal (M) atom. KEY WORDS : Hofmann type clathrates, Vibrational spectra, 4-Phenylpyridine, 1,4-Dioxane Bull. Chem. Soc. Ethiop. 2010 , 24(3), 375-381.

Vibrational spectroscopic studies of some dimethylpyrazine cadmium (II) tetracyanonickelate benzene clathrates: [Cd(C6H8N2)Ni(CN)4]·C6H6

Two new cadmium dimethylpyrazine (2,3-dimethylpyrazine or 2,5-dimethylpyrazine) tetracyanonickelate benzene clathrates, [Cd(C6H8N2)Ni(CN)4]·C6H6, have been prepared in powder form and characterized by FT-IR spectroscopy, Raman spectroscopy, X-ray diffraction, thermal analyses and elemental analyses. Vibrational assignments are proposed for the bands of the host lattice and guest molecule. It is shown that the spectra are consistent with a proposed crystal structure for these compounds derived from X-ray diffraction measurements. The C, H, N, Cd and Ni analyses were carried out for all the compounds. Thermal behaviors of these compounds are followed using TG and DTA techniques. The FT-IR, Raman spectroscopic, XRD, thermal and elemental analyses results propose that these compounds are similar in structure to the Hofmann-type clathrates. Their structure consists of planar polymeric layers, {M–Ni(CN)4}∞, formed from Ni(CN)4 anions coordinated to the bridging 2,3- or 2,5-dimethylpyrazine molecules bound directly to the cadmium. The cadmium atoms are bound to four N atoms of the CN ions and, the Ni atoms are surrounded by four C atoms of the CN groups in a square-planar layer.

FT-IR spectroscopic study on some Hofmann-type clathrates: M( p-Benzoquinone)Ni(CN) 4·2G (M = Mn, Co, Ni or Hg; G = Aniline)

Some new Hofmann type aniline clathrates in the form of M( p-Benzoquinone)Ni(CN) 4·2G (M = Mn, Co, Ni or Hg, p-Benzoquinone = pBQ and G = Aniline = An) have been obtained for the first time in powder form and their FT-IR spectra have been reported in the range of (4000–400) cm −1. The thermal behavior of these clathrates has been also investigated by thermo-gravimetric analysis (TGA), differential thermal analysis (DTA) and derivative thermal gravimetric analysis (DTG). The spectral and thermal analysis results of the new Hofmann type aniline clathrates suggest that the obtained clathrates are new examples of the Hofmann-type clathrates. The Hofmann-type clathrates consist of the corrugated |M–Ni(CN) 4| ∞ polymeric layers which are held in parallel through the chain of (-M-pBQ-M-pBQ-) in our new Hofmann type aniline clathrates formed by bounding electrons of oxygen atoms of the carbonyl groups of pBQ ligand to transition metal atoms.

Vibrational spectroscopic study on some Hofmann type clathrates: M(1-Phenylpiperazine) 2Ni(CN) 4·2G (M = Ni, Co and Cd; G = aniline)

New Hofmann type aniline clathrates in the form of M(pp) 2Ni(CN) 4.2G (where pp = 1-phenylpiperazine, G = aniline and M = Ni, Co and Cd) have been prepared in powder form and FT-IR and Raman spectra have been reported. The thermal behaviour of these clathrates has been investigated by thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). The results suggest that these compounds are similar in structure to the Hofmann type clathrates and their structures consist of corrugated polymeric layers of | M–Ni(CN) 4 | ∞ with the pp spanned between two metal (M) atoms, of the consecutive two layers.

Hofmann type clathrates – spectroscopic studies of the low frequency region

A series of Hofmann type clathrates with a general formula: M(NH 3) 2M′(CN) 4·2G, where M ∈ {Ni, Mn, Cd}, M′ ∈ {Ni, Pd}, while G is benzene or thiophene, were prepared and their Raman and far-infrared spectra were recorded in the region 650–50 cm −1. The main bands of the vibrational spectra in the low frequency region were assigned to the stretching and deformational vibrations: ν(Ni–C)/ ν(Pd–C), δ(NiCN)/ δ(PdCN), π(NiCN)/ π(PdCN), δ(CNiC)/ δ(CPdC), ν(M–N) and δ(NMN) originating from the host lattices: M(NH 3) 2Ni(CN) 4 or M(NH 3) 2Pd(CN) 4. The Raman and far-infrared spectra of the studied Hofmann type clathrates were compared with the corresponding spectra of K 2Ni(CN) 4 and K 2Pd(CN) 4 as well as with Ni(NH 3) 6Cl 2, and in some cases, with the spectra of the “empty” clathrates.

FT-IR spectroscopic study of the Hofmann type clathrates: M(4-Chpy) 2 Ni(CN) 4· nG (M = Ni or Co; G = 1.4-dioxane)

New Hofmann type clathrates in the form of M(4-Chpy) 2Ni(CN) 4· nG [where 4-Chpy = 4-(3-cyclohexen-1-yl)pyridine, G = 1,4-dioxane and M = Ni, Co] were prepared in powder form and their infrared spectra are reported in the range of 4000–400 cm −1. The spectral features point out that the compounds are similar in structure to the Hofmann type clathrates. Regarding host–guest interaction, the interaction for the present compounds is weak resulting from the large cavity of the host structure.

FT-IR Spectroscopic Study of M(1,2-Ethanedithiol)Ni(CN)4·Benzene (M=Co,Cd) Clathrates

New Hofmann-ethanedithiol-type clathrates, M(1,2-Ethanedithiol)Ni(CN)4·Benzene (M=Cd,Co), have been obtained in the powdered form. By vibrational spectroscopy of these two new compounds, it is exhibited that their structures are similar to those of the other Hofmann-type clathrates.

IR Spectroscopic Study of M(Benzoic Acid)2Ni(CN)4·(1,4-Dioxane) Clathrate (M = Ni, Cd and Co)

In this study, clathrate of benzoic acid-tetracyanonickel, given by the formula M(benzoic acid)2Ni(CN)4・(1,4-dioxane) (M = Ni, Cd and Co), is obtained for the first time through chemical methods. The similarities of the observed spectra indicate that the obtained clathrate of benzoic acidtetracyanonickel is a new example of Hofmann-type clathrates. - PACS numbers: 33.20.Ea, 33.20.Tp

Ft-Ir Spectroscopic Study Of Co(1-Propanethiol)2Ni(Cn)4·Benzene Clathrate

By vibrational spectroscopy of the new Hofmann-propanethiol-type clathrate Co(1-propanethiol) 2Ni(CN)4·Benzene it is shown that its structure is similar structure to those of other Hofmanntype clathrates.

An infrared and Raman spectroscopic study of the Hofmann-type complexes and clathrates: M(piperidine) 2Ni(CN) 4; M(piperidine) 2Ni(CN) 4·1.5G (M=Cd, Co, Ni or Cu; G=benzene)

New Hofmann-type complexes and clathrates of the forms M(piperidine) 2Ni(CN) 4 and M(piperidine) 2Ni(CN) 4·1.5G (M=Cd, Co, Ni or Cu; G=benzene) were prepared in powder form and their infrared and Raman spectra are reported. The spectral features suggest that these compounds are similar in structure to the Hofmann-type clathrates except for the copper compounds. The complex and clathrate of Cu have different spectral features in comparison with its analogues due to the Jahn-Teller effect.