Three-Dimensional Framework Constructed Using Nanometer-Sized Metallamacrocycle as a Secondary Building Unit

Abstract

Research on microporous structures has concentrated largely on inorganic materials such as aluminosilicates and aluminophosphates. 1 The assembly of microporous materials from organic molecule and metal ion building blocks is an emerging area that is yielding new generations of open supramolecular architecture. 2 An important strategy for the construction of metal-organic open framework structures concerns the self-assembly of the appropriate metal salts and a tailored ligand in an appropriate solvent. However, nature tends to avoid a vacuum, and identical copies interpenetrate to fill the space. 3 The design and synthesis of new framework materials containing large pores is a continuous challenge. A new strategy for the construction of a microporous material is to use inorganic clusters as secondary building units in the assembly of the extended networks. 4 In this study, we tried to construct a new open framework structure using a large organic-inorganic hybrid secondary building unit that would prevent the interpenetration of identical copies.We have recently synthesized a nanometer-sized hexanuclear manganese metallamacrocycle using a chelating pentadentate ligand. 5 Each metal center in the hexanuclear manganese metallamacrocycle has been coordinated by five donor atoms from two chelating pentadentate ligands and an additional donor atom from a solvent molecule. Three solvent molecules coordinated at the metal centers are in one face of the cluster, and the other three solvent molecules coordinated at the other metal centers are in the other face of the cluster. In this study, we have tried to synthesize a new open framework material using a nanometersized rigid building block. We exchanged the coordinated solvent molecules of the metallamacrocycle using an exobidentate ligand to construct a three-dimensional framework.When an N-acetylsalicylhydrazidate (ashz 3-) was used as a pentadentate ligand for an octahedral manganese(III) ion and a 1,2-bis(4-pyridyl)ethane (bpea) was used as an exobidentate ligand, a self-assembled three-dimensional molecular open framework was easily constructed. 6 The hexanuclear manganese metallamacrocycle served as a discrete molecular building block, and the exobidentate ligand bpea connected the building block. A diagram of the open framework [Mn 6 (ashz) 6 (DMF) 2 (bpea) 2 ] n (1) is shown in Figure 1. 7 The building block, hexanuclear manganese metallamacrocycle [Mn 6 (ashz) 6 ], was similar to the previously reported hexanuclear manganese metallamacrocycle [Mn 6 (fshz) 6 (MeOH) 6 ]. 5 All building blocks were connected by exobidentate ligands, where the intermetal distance spaced by an exobidentate ligand was about 13.8 Å. The framework has four nanometer-sized channels along the crystallographic c axis per unit cell (Figures 1 and 2). Many solvent molecules were packed into the channels in the crystal structure. The framework was estimated to occupy only about 51% of the crystal volume by the PLATON program. 8 The average van der Waals diameter of the solvent channels w...

Novel 24-membered octanuclear manganese(III) metallacrown

“…They have also been used as building blocks for the construction of two-or three-dimensional network structures [4]. A variety of metallamacrocycles and cages were found to form interesting hostguest systems with different metal ions of varying coordination and symmetry [5].…”

Novel 18-membered hexanuclear metallamacrocycle: Synthesis, crystal structure, and magnetic properties

“…The novel 18-metallacrown-6 metallamacrocycle, with the formula of [Mn 6 (amshz) 6 (CH 3 OH) 6 ]Á6H 2 O (amshz = N-acetyl-3-methyl-salicylhydrazide), has been prepared and characterized. Six Mn(III) ions and six deprotonated N-acetyl-3-methyl-salicylhydrazide (amshz 3À ) ligands construct a planar 18-membered ring based on Mn-N-N-Mn linkage.…”

“…The magnetic properties of the metallacrown molecules are characterized by a weak antiferromagnetic exchange interaction, with l eff = 5.12 l B at 300 K between the Mn 3+ ion spins with S = 2 in the cyclic system. Growing interest in the rational design and construction of metallamacrocycles is motivated principally by their diverse molecular architectures [1][2][3], their utilization as motifs for coordination networks [4][5][6][7][8] and their potential as host systems in various guest recognition chemistries [9][10][11][12][13][14][15]. Metallacrowns known as the first of a new class of metallamacrocycles, have been readily assembled using a trianionic pentadentate ligand, N-acylsalicylhydrazide, with a trivalent octahedral metal ion such as manganese, iron, cobalt or gallium [16][17][18].…”

“…Herein, We designed a potential pentadentate ligand N-acetyl-3-methyl-salicylhydrazide [20] (H 3 amshz, Scheme 1) used in the preparation of a novel manganese(III) 18-metallacrown-6 compound, [Mn 6 (amshz) 6 (CH 3 OH) 6 ]Á 6H 2 O [21]. The ligand N-acetyl-3-methyl-salicylhydrazide was synthesized by reacting acetic anhydride (2.0 g, 20.0 mmol) with 3-methyl-salicylhydrazide (3.1 g, 18.0 mmol) in DMF (20 mL) at 0°C, then slowly warmed to room temperature and stirred for 2 h. After leaving overnight in a refrigerator, the resulting white precipitate was filtered and rinsed with chloroform and diethyl ether.…”

Self-assembly of a two-dimensional cluster coordination polymer {[W2S8Cu8I4(bpe)2(py)2]·H2O}n: Crystal structure and luminescent properties

“…The network displays a (4, 4) topology if considering the SBUs as the nodes, which is similar to a Zn(II) coordination polymer with dinuclear motif as nodes [42]. The flexible bidentate ligand 1,2-bis(4-pyridyl)ethane, which is not like rigid bidentate ligand 4,4 0 -bipyridine, can adopt anti or gauche conformations [43][44][45][46][47]. The bpe ligand are all gauche-form in compound 1, and the torsion angles about the ethyl bond in bpe are À45.6(1) and 65.2(1)°, respectively.…”