Dual Behavior of Bromine Atoms in Supramolecular Chemistry: The Crystal Structure and Magnetic Properties of Two Copper(II) Coordination Polymers

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• 作者：Firas F. Awwadi ; Roger D. Willett ; Brendan Twamley ; Mark M. Turnbull ; Christopher P. Landee
• 刊名：Crystal Growth & Design
• 出版年：2015
• 出版时间：August 5, 2015
• 年：2015
• 卷：15
• 期：8
• 页码：3746-3754
• 全文大小：495K
• ISSN：1528-7505

文摘

The crystal structures of two copper(II) chloride coordination polymers, (Cu₂(2bp)₂Cl₄)n, henceforth 鈥減olydimer鈥? and (Cu₃(2bp)₂Cl₆)n, henceforth 鈥減olytrimer鈥? where 2bp = 2-bromopyridine, and the temperature dependence of their magnetic susceptibilities are reported. Also, the temperature dependence of the magnetic susceptibility of the monomeric complex, Cu(2bp)₂Cl_2, is reported. The magnetic data were measured in the range 2鈥?10 K. The organic bromine atom of the 2bp ligand shows electrophilic and nucleophilic character: an electrophilic nature via C鈥揃r路路路Cl interactions and a nucleophilic nature via Cu路路路(蟺)Br interactions. The Cu路路路(蟺)Br interactions, previously underestimated in the literature, turn the 2bp ligand to a bidentate rather than monodentate ligand via the N鈥揅u coordination bond and the Cu路路路(蟺)Br noncovalent interactions. Thus, the 2bp ligand behaves as a molecular bender; the Cu路路路(蟺)Br interactions result in the bending of the (CuCl₂)n infinite linear extended chains at specific locations. The magnetic data of the monomer were fit to the two-dimensional S = 1/2 Heisenberg model (Curie constant = 0.43(1) emu-K/mol-Oe and an exchange constant J/k = 0.41(4) K). The magnetic data of the polydimer were best fit to an alternating antiferromagnetic chain rather than a dimer model (Curie constant = 0.415(3), J₁/k = 鈭?1.4(1) K, J(2)/k = 鈭?.2(3) K). The magnetic data of the polytrimer may be approximated by a model including both nearest neighbor (J₁) and next nearest neighbor (J₂) interactions within the polytrimer as well as a Curie鈥揥eiss correction for intertrimer exchange within a single chain [J₁ = 鈭?3(1) K, J₂ = 鈭?.0(5) K, 胃 = 鈭?.5(5) K]. Viewing the reported structures as bent coordination polymers is supported by observations that (a) the Cu路路路Cl coordination distance is quite short (avg. = 2.672 脜) and (b) the magnetic data of the polydimer are best fit to the alternating antiferromagnetic chain model.