Abstract
Using the structural and electronic tunability of molecules to control magnetism is a central challenge of inorganic chemistry. Herein, a ten-member family of the high-ordering temperature (Tc) molecule-based magnetic coordination networks of the form V[x-ClnPTCE]2·yCH2Cl2 (PTCE = phenyltricyanoethylene, y < 0.5) were synthesized and characterized, where x is (are) the position(s) and n is the number of chlorine substitutions on the phenyl ring. These chlorophenyltricyanoethelenes are tunable analogs of the more commonly investigated tetracyanoethylene (TCNE). Varying the number and position of chlorine substitution around the phenyl ring engendered a family of network solids with significantly different magnetic ordering temperatures ranging from 146 to 285 K. The Tcs of these ferrimagnets were rationalized with the aid of cyclic voltammetry and Density Functional Theory (DFT) calculations.
Highlights
IntroductionThe ferrimagnet V[TCNE]2·yCH2Cl2 (where y < 0.5) was discovered in 1991, and improved syntheses have yielded samples with ordering temperatures (or critical temperatures, Tcs) up to 400 K [1,2,3]. As a room temperature magnetic semiconductor, films of V[TCNE]2 show potential for application in spintronics [4,5], a point emphasized by the extremely narrow ferromagnetic resonance spectra [6]
The ferrimagnet V[TCNE]2·yCH2Cl2 was discovered in 1991, and improved syntheses have yielded samples with ordering temperatures up to 400 K [1,2,3]
Efforts by us and others to tune the properties of V[TCNE]2-like magnets have involved the preparation of compounds with other transition metal ions [7], combinations of metal ions [8,9], and other conjugated polynitriles [10,11,12,13,14,15,16,17]
Summary
The ferrimagnet V[TCNE]2·yCH2Cl2 (where y < 0.5) was discovered in 1991, and improved syntheses have yielded samples with ordering temperatures (or critical temperatures, Tcs) up to 400 K [1,2,3]. As a room temperature magnetic semiconductor, films of V[TCNE]2 show potential for application in spintronics [4,5], a point emphasized by the extremely narrow ferromagnetic resonance spectra [6]. The Tcs of the V[x-FnPTCE]2 networks displayed a significant dependence on the position of the fluorine substitution, and the trend was rationalized using a combination of steric and electronic effects based on electrochemical and computational data. Comprehensive and systematic magnetochemical studies of this kind offer insight into the factors that govern magnetic ordering within V[TCNE]2-like magnets, with the aim of eventually exploiting these factors to develop improved, higher-Tc materials. We extend these substituent-effect studies to analogous magnets of the form V[x-ClnPTCE]2. We were interested in investigating the change in electronegativity between F and Cl to compare the impacts on Tc by the positional electronic effects of each halogen substitution. In order to facilitate these comparisons, ten new chlorophenyltricyanoethylene one-electron acceptors (Figure 1) were synthesized, the magnetic
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