Microwave versus Traditional Solvothermal Synthesis of Ni₇^II Discs: Effect of Ligand on Exchange Reaction in Solution Studied by Electrospray Ionization-Mass Spectroscopy and Magnetic Properties

Abstract

A comparative evaluation of the solvothermal method of synthesis of magnetic Ni(7) discs with four different ligands using the same concentrations of reagents and temperature found microwave heating is more effective than the traditional oven one. Where the former only needs minutes, the latter needs days with an equivalence of 10 min microwave to 1 day of traditional. The size of crystals has a narrow distribution and increases with time for the microwave but is a rather wide distribution for the traditional one. Furthermore the shape of the crystals is more regular for the microwave. The four Ni(7)(II) discs of formulas [Ni(7)L(6)(μ(3)-OMe)(6)](ClO(4))(2) (1-3) and {[Ni(7)(L(4))(6)(μ(3)-OMe)(6)][Ni(L(4))(2)]}(ClO(4))(2) (4) were synthesized as green hexagonal rods from Ni(ClO(4))(2)·6H(2)O in mixed MeOH/MeCN solution and salicylalde Schiff base ligands (L(1) = 2-methoxy-6-(iminomethyl)phenol, L(2) = 2-ethoxy-6-(iminomethyl)phenol, L(3) = 2-methoxy-6-((methylimino)methyl)phenol, L(4) = 2-ethoxy-6-((methylimino)methyl)phenol). X-ray structural analyses show six symmetrically positioned Ni(2) around a central Ni(1) bridged by the μ(3)-methoxide and surrounded by the ligand L which also isolates the discs from one another. The perchlorate sits in the interstices, and the planar [Ni(L(4))(2)] of 4 also inserts itself between the discs. The structures of 1-3 can be regarded as ordered discotic liquid crystals. Electrospray ionization mass spectrometry of solutions showed an exchange of methoxide for hydroxide and a different distribution of [Ni(7)] phase with mixed (MeO/OH) core bridges, confirming a probable "step by step" substitution of MeO(-) by OH(-). Magnetic studies indicate ferromagnetic interaction between Ni(1) and Ni(2) and possible antiferromagnetic between Ni(2) and Ni(2), resulting in a noncollinear system which only reaches half of the moment in 50 kOe at 2 K.

Six Isomorphous Window‐Beam MOFs: Explore the Effects of Metal Ions on MOF‐Derived Carbon for Supercapacitors

“…The axial positions are occupied by two water molecules with a bond length of 2.085(3) Å. Ni2 lies in a distorted octahedral coordination sphere, which is composed of two chelating carboxylic groups (O1‐C25‐O2 and O3‐C26‐O4), one syn‐anti carboxylic group (O5‐C27‐O6) and one imidazole ring of bibp. The coordination bond lengths of Ni2−O range from 2.053(3) to 2.232(3) Å, and Ni2−N distance is 2.031(3) Å, which are all comparable with those observed in related Ni II polymeric structures (Table S1 in Supporting Information) …”

“…The coordinationb ond lengths of Ni2ÀOr ange from 2.053(3) to 2.232(3) ,a nd Ni2ÀNd istance is 2.031(3) , which are all comparable with those observed in related Ni II polymericstructures (Table S1 in Supporting Information). [27,28] The fully deprotonatedb tc 3À ion bridges four Ni II ions with two bidentate chelating and one syn-anti carboxylic groups. The Ni2 ion is connected by btc 3À to form a2 Da nionic layer {[Ni(btc)] À } 1 (Figure 1b).…”

Stepwise Assembly of MII7 Clusters Revealed by Mass Spectrometry, EXAFS, and Crystallography

“…The cluster Ni 7 crystallizes in the trigonal system with space group P c 1. The molecular cluster has previously been described as a double‐calix unit with the metal hydroxide brucite segment plane in the middle (Supporting Information, Figure S2) . Within the structure, the clusters adopt a hexagonal arrangement, with the perchlorate ions filling the space in between, and forming N−H⋅⋅⋅O bonds.…”

Iterative Mass Spectrometry and X-Ray Crystallography to Study Ion-Trapping and Rearrangements by a Flexible Cluster

“…The polydentate Schiff-base ligand has an interesting laboratory of binding sites where all the coordinating atoms are placed on one side of the molecule segregating the clusters on formation333436. The N(imine)-O(hydroxy) and a O(hydroxy)-O(methoxy) can only chelate while the sulfonate has chelating, bridging as well as terminal coordination functionalities.…”

“…Electrospray Ionisation Mass spectrometry (ESI-MS) is an alternative technique to study such transformation171829303132. In particular, ESI-MS is very useful when the metals are paramagnetic, rendering NMR difficult3334. In this work, we describe the chemistry of a flexible cluster in solution using ESI-MS and single-crystal X-ray diffraction(SCXRD) iteratively to follow the reactions towards ion-trapping and the rearrangements of the ligands, the incorporated solvents and the central inorganic core.…”