Effect of ethylenediamine on the formation of macro, micro, and nanostructures based on [W^VI(Cat)₂O₂]²⁻

Abstract

We synthesized yellow needle-shaped crystals of IJNH 3 CH 2 CH 2 NH 3 ) 0.5 IJNH 3 CH 2 CH 2 NH 2 )ij(Cat) 2 W VI IJO) 2 ] ·IJNH 2 CH 2 CH 2 NH 2 ), 1, with a one-dimensional chain-like quantum motif, and red bulk crystals of IJNH 3 CH 2 CH 2 NH 2 ) 2 ij(Cat) 2 W VI IJO) 2 ], 2, with a multi-tubular quantum unit, by a slight change in the degree of protonation of ethylenediamine. By grinding and ultra-sonication, crystal 1 disintegrated into nanowires with diameters of about 18 nm and lengths of 300-1000 nm, and crystal 2 disassembled into nano-tubules with diameters of 15-18 nm and lengths of 450-550 nm. We found that the quantum motifs of the crystal lattices are a template of the nanostructures i.e. quantum-chains induced the formation of nanowires and quantum-tubules led to the production of nano-tubules. To investigate the mechanism by which such a delicate change of ethylenediamine can cause such a great transformation in the nanostructure, nanopipe-bundles (rather than nanowires) prepared from crystal 3 were used as a comparison. Although crystals 3 and 1 have similar crystal parameters, they contain different ethylenediamine moieties i.e. 3 is IJNH 3 CH 2 CH 2 NH 2 ) 2 ij(Cat) 2 W VI IJO) 2 ]·IJNH 2 CH 2 CH 2 NH 2 ). As is well known, the electrostatic attraction of the doubly-protonated cation IJNH 3 CH 2 CH 2 NH 3 ) 2+ to the anion ij(Cat) 2 W VI IJO) 2 ] 2− is stronger than that of the neutral molecule NH 2 CH 2 CH 2 NH 2 . The ij(Cat) 2 W VI IJO) 2 ] 2− -based chains were induced to split in various manners by different protonated ethylenediamines, thereby manufacturing different nano-architectures. This paper reveals that slight changes in the protonation of ethylenediamine can induce nanostructures assembled from ij(Cat) 2 W VI IJO) 2 ] 2− to form a variety of morphologies and sizes. We have proposed a new idea and method to prepare quite different tungsten organic hybrid nanostructures by changing the degree of protonation of ethylenediamine.(i.e. the nano-species is constructed using atoms or molecules). However, a controlled and reproducible preparation of such nano-species still needs to be achieved and their formation mechanisms are not yet clarified. In previous papers, 32-39 we designed a series of bulk crystals constructed of Mo-and W-based coordinated structures. Furthermore, by milling and ultrasonication, we disassembled the single crystals into nanowires, nanoparticles, nano-tubules and nanoribbons. In particular, we prepared different nanostructures from bulk crystals of ij(Cat) 2 W VI IJO) 2 ] 2− that combined with protonated ethylenediamine, protonated 1,2-propanediamine, and protonated 1,3-propanediamine, respectively. 40 In addition, we demonstrated in the paper that the morphology of the nano-aggregates was related to the quantum motif of their crystal lattice; for instance, quantum-spots induced the formation of nanoparticles, quantum-wires prompted the production of nano-ribbons, etc. To study further this effect, two tungsten containing single crystals ijNH 3 CH 2 CH 2 NH 2 ] 2 ijW VI O 2 IJO 2 C 6 H 4...