T5 Clusters Research Articles

Consolidation of 2D Frameworks Based on Corner-Shared Supertetrahedral T5 Clusters via M2OS2 Units for Tunable Photoluminescent and Semiconductor Properties.

Introducing transition metals into the intercluster linkers has been considered an important strategy for the rapid development of metal chalcogenide supertetrahedral (Tn) cluster-based open frameworks with excellent properties. However, using this strategy for achieving the structure and property tunability in the cluster-based framework of Tn (n ≥ 5) is still a great challenge. Herein, we report on three new sulfide and oxosulfide open frameworks of T5 clusters, i.e., T5-ZnMnInOS ([In30Zn5Mn4O2S58]12-), T5-MnInOS ([In34Mn5O2S58]8-), and T5-MnInS ([In28Mn6S54]12-). Interestingly, transition metals Zn and Mn are successfully introduced into T5-ZnMnInOS and T5-MnInOS via the consolidation of corner-shared Zn2OS2 and Mn2OS2 units, respectively. Under the photoexcitation of UV light, three compounds can emit bright-orange-red light closely associated with the Mn2+ ions, and the compounds containing M2OS2 units exhibit better photoluminescence (PL) lifetimes. Variable-temperature PL spectra demonstrate that the introduced M2OS2 units are favorable for weakening the deformation of the skeleton structure and decreasing the red shifts of the emission peaks at low temperatures. Moreover, the experimental results exhibit that the three compounds are wide-band-gap semiconductors and that the photogenerated electron separation efficiency can be doubly increased because the intercluster linkers are fixed by the M2OS2 units. This work paves a new way for enriching the content and distribution types of transition-metal sites in the supertetrahedral cluster-based metal chalcogenide open frameworks.

Hybrid Assembly of Different-Sized Supertetrahedral Clusters into a Unique Non-Interpenetrated Mn-In-S Open Framework with Large Cavity.

Reported here is a unique crystalline semiconductor open-framework material built from the large-sized supertetrahedral T4 and T5 clusters with the Mn-In-S compositions. The hybrid assembly between T4 and T5 clusters by sharing terminal μ2-S2- is for the first time observed among the cluster-based chalcogenide open frameworks. Such three-dimensional structure displays non-interpenetrated diamond-type topology with extra-large nonframework volume of 82%. Moreover, ion exchange, CO2 adsorption, as well as photoluminescence properties of the title compound are also investigated.

Ionothermal synthesis of discrete supertetrahedral Tn (n = 4, 5) clusters with tunable components, band gaps, and fluorescence properties.

The preparation of crystalline molecularly supertetrahedral Tn clusters with variable sizes and components is of vital importance for the fundamental study of their physicochemical properties. However, setting up an efficient method to stabilize large discrete Tn clusters is a challenge due to their high negative charges and polymerization nature. In this work, we report on the ionothermal synthesis of three discrete T4 cluster compounds, namely [Bmmim]5[(CH3)2NH2]4[NH4][M4In16S31(SH)4]·6H2O (M = Mn (1), Zn (2), Cd (3), Bmmim = 1-buty-2,3-dimethyl-imidazolium), and four discrete T5 cluster compounds, namely [Bmmim]10[NH4]3[Cu5Ga30-xInxS52(SH)4] (x = 6.6 (5), 14.5 (6), 23.8 (7), and 30 (8)). The compound [Bmmim]10[NH4]3[Cu5Ga30S52(SH)4] (4) previously reported by us features a discrete T5 cluster. The steep UV-Vis absorption edges indicate band gaps of 2.20 eV for 1, 2.64 eV for 2, 2.69 eV for 3, 3.04 eV for 4, 2.65 eV for 5, 2.48 eV for 6, 2.32 eV for 7, and 2.30 eV for 8. The compositions of T5 clusters could be varied with the ratios of Ga : In in the starting reagents, providing an opportunity to systematically control the band gaps and fluorescence performances of T5 cluster-based compounds. This research might advance the understanding of the ionothermal preparation and functionality tuning of crystalline chalcogenides.

Assembly of supertetrahedral clusters into a Cu–In–S superlattice via an unprecedented vertex–edge connection mode

We demonstrated the first case of a vertex–edge inter-cluster connection mode in a three-dimensional open-framework chalcogenide built from the largest known T5 cluster.

Discrete supertetrahedral CuInS nanoclusters and their application in fabrication of cluster-sensitized TiO2photoelectrodes

Supertetrahedral nano-CuInS clusters are prepared and the crystals can instantly dissolve in a solution having high ionic strength to create a solution with uniform T5 clusters. The nano-CuInS clusters can be easily wet-modified on a TiO2electrode and show excellent photo-sensitive properties.

Hydrothermal syntheses and characterization of two tetramethylammonium templated indium sulfides

Two indium sulfides [(Me)4N]6[In10S18] (1) and [(Me)4N]13[Cu5In30S54] (2) have been hydrothermally synthesized. Compound 1 is a 3D open framework built from T3 clusters, which has large porosity. Compound 2 has a double-layered structure constructed by T5 clusters. Our results indicate that tetramethylammonium ion is an efficient structure-directing agent for both ternary and quaternary indium sulfides. The optical and thermal properties have also been investigated.

Coassembly between the Largest and Smallest Metal Chalcogenide Supertetrahedral Clusters

Reported here is the first crystalline inorganic-organic hybrid material combining In, Ge, and Cu. The trimetallic system undergoes a nanoscale separation into small In-Ge-S supertetrahedral T2 clusters and large In-Cu-S T5 clusters, which are further assembled into a T2-T5 mixed layer. This material reveals the long-range crystallographically ordered assembly from supertetrahedral clusters with 3 orders of difference, the largest size mismatch known so far for mixed-supertetrahedral-cluster materials. Theoretical simulations were performed to probe the contribution to the band structure by the different-sized semiconducting clusters.

Superbase Route to Supertetrahedral Chalcogenide Clusters

Supertetrahedral Tn clusters are exact fragments of a cubic ZnS type lattice. Thus far, Tn clusters up to T4 with 20 metal sites can be synthesized in a discrete molecular form. Yet, synthesis of larger discrete supertetrahedral clusters still remains a great challenge, likely due to the rapidly increasing negative charge on the cluster as the size goes up. By using organic superbases (DBN and DBU) to help stabilize the negative charge, a family of discrete supertetrahedral chalcogenide clusters with sizes spanning from T3 (10 metal sites) to T5 (35 metal sites) have been made. The T5 cluster represents the largest molecular supertetrahedral Tn cluster known to date.

Largest discrete supertetrahedral clusters synthesized in ionic liquids

Four discrete T5 cluster compounds with Cu–M–S constituents (M = In for compound 1, Ga for 2–4) have been synthesized in an ionic liquid (IL) [Bmmim]Cl (Bmmim = 1-butyl-2,3-dimethyl-imidazolium), which represent the largest molecular clusters in a Tn series. The in situ decomposition of the IL generates the Bim ligand (Bim = 1-butyl-2-methyl-imidazole) that directly coordinates to some of the corner Ga3+ ions of the T5 clusters in 3–4, leading to the formation of the first inorganic–organic hybrid T5 clusters. 2–4 show significantly broad photoluminescent emission bands ranging from 500 to 800 nm with a full width at half maximum (fwhm) at about 180 nm. This research provides a new method for synthesizing molecular metal chalcogenides that uses ILs as a reactive solvent and stabilizer.

A Large Indium Sulfide Supertetrahedral Cluster Built from Integration of ZnS-like Tetrahedral Shell with NaCl-like Octahedral Core

An entirely new type of chalcogenide cluster and a new structural mechanism for the formation of large semiconducting tetrahedral clusters have been revealed as a result of crystallization of a templated indium sulfide consisting of an unprecedented cluster, In(38)S(65), which is the largest supertetrahedral cluster based on trivalent metal ions. At the core of this cluster is In(10)S(13), which can be considered as a fragment of the NaCl-type lattice. The In(10)S(13) cluster is coupled to four In(4)S(10) supertetrahedral T2 clusters and four In(3)S(3) hexagonal rings to give In(38)S(65), which is also the largest inorganic chalcogenide supertetrahedral cluster, superseding a supertetrahedral T5 cluster with only 35 metal sites.

Theoretical Simulation of n-Alkane Cracking on Zeolites

The kinetics of alkane cracking in zeolites MFI and FAU have been simulated theoretically from first principles. The apparent rate coefficient for alkane cracking was described as the product of the number of alkane molecules per unit mass of zeolite that are close enough to a Bronsted-acid site to be in the reactant state for the cleavage of a specific C-C bond and the intrinsic rate coefficient for the cleavage of that bond. Adsorption thermodynamics were calculated by Monte Carlo simulation and the intrinsic rate coefficient for alkane cracking was determined from density functional theory calculations combined with absolute rate theory. The effects of functional, basis set, and cluster size on the intrinsic activation energy for alkane cracking were investigated. The dependence of the apparent rate coefficient on the carbon number for the cracking of C3-C6 alkanes on MFI and FAU determined by simulation agrees well with experimental observation, but the absolute values of the apparent rate coefficients are a factor of 10 to 100 smaller than those observed. This discrepancy is attributed to the use of a small T5 cluster representation of the Bronsted-acid site. Limited calculations for propane and butane cracking on MFI reveal that significantly better agreement between prediction and observation is achieved using a T23 cluster for both the apparent rate coefficient and the apparent activation energy. The apparent rate coefficients for alkane cracking are noticeably larger for MFI than FAU, in agreement with recent findings reported in the experimental literature.

Crystal of Semiconducting Quantum Dots Built on Covalently Bonded T5 [In28Cd6S54]‐12. The Largest Supertetrahedral Cluster in Solid State.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Crystal of semiconducting quantum dots built on covalently bonded t5 [in(28)cd(6)s(54)](-12): the largest supertetrahedral cluster in solid state.

Periodic array of nanoparticles is essential for practical applications in optical devices. Periodic dot arrays often exhibit very interesting collective phenomenon. We report a periodic crystal of InCdS pseudo-T5 nanocluster, the largest supertetrahedral cluster found thus far in solid state. Each InCdS cluster behaves like a nanoparticle with the same size. Unlike the array of colloidal dots in which the dot-dot separation is large ( approximately 5 nm), the neighboring T5 clusters in [In28Cd6S54].[(CH3)4N]12[(HSCH2COOH)2]3.5 crystal form a natural point contact by sharing covalently bonded S atoms. Both experimental and theoretical studies show that this crystal is a semiconductor with a band gap of 3.0 eV.

Nanocluster with one missing core atom: a three-dimensional hybrid superlattice built from dual-sized supertetrahedral clusters.

In addition to having size-dependent properties, nanoclusters also behave like large pseudo-atoms and serve as building blocks for the construction of superlattices with properties that differ from either individual clusters or the bulk. While colloidal nanoparticles usually self-assemble into close-packed lattices, supertetrahedral clusters that are regular fragments of the zinc blende-type lattice can form covalent lattices with large pore size and high pore volume. Unfortunately, the size of the known supertetrahedral cluster is still small, and only a few types are currently known. In addition, their superlattices invariably consist of clusters of identical size. Here we report an open framework sulfide (denoted as UCR-15) that extends the cluster size from 20 metal ions in a T4 supertetrahedron to 34 metal ions in a novel T5 supertetrahedron with a missing core atom, [In34S54]6-. T5 clusters are joined by smaller T3 clusters (i.e., [In10S18]6-) to form an extended superlattice. UCR-15 is the first example of a covalent open framework built from supertetrahedral clusters of different sizes, thus revealing new possibilities in the construction of crystalline nanoporous semiconducting superlattices. It is proposed here that the formation of the dual-sized T3 and T5 hybrid framework is related to the host-guest charge density matching.

A density-functional study of the dehydrogenation reaction of isobutane over zeolites

The dehydrogenation reaction of isobutane over zeolites was investigated at the B3LYP/6-31G ∗∗ and 6-311G ∗∗ levels of calculation, and with T3 and T5 clusters representing the zeolite. The transition state (TS) exhibits a carbenium ion-like character, and the activation energy, at the best level of theory, is 53.4 kcal/mol. Contrary to what has been previously proposed, IRC calculations show that the mechanism does not involve the formation of alkoxide, but rather the carbocation collapses directly into isobutene while the eliminated proton, restores the zeolite's acid site. Increasing the size of the cluster and of the basis set does not change the mechanism.