Diamagnetic Molecules Exhibiting Room-Temperature Ferromagnetism in Supramolecular Aggregates

Abstract

Molecule-based materials exhibiting room-temperature ferromagnetism and semiconducting property are promising for molecular spintronic applications. Chemically tunable electronic and magnetic properties of metallo-phthalocyanine (MPc) molecules make them potential candidates in the frame. Here, we show room-temperature ferromagnetism in supramolecular aggregates of two diamagnetic MPcs, nickel(II) phthalocyanine (NiPc; S = 0) and zinc(II) hexadecafluorophthalocyanine (ZnFPc; S = 0). In the magnetization versus applied field (M−H) plot, recorded at room temperature, the supramolecular NiPc•••ZnFPc aggregate revealed a clear hysteresis loop with coercive field (H c ) of ∼180 Oe. The H c values were further increased with decreasing the temperature down to 95 K. The direct current (DC) electrical conductivity value of the supramolecular NiPc•••ZnFPc system was observed to be significantly higher than that of a mechanical mixture of NiPc+ZnFPc. An optical band gap of ∼1.25 eV for the supramolecular solid was estimated from the Tauc plot, and no appreciable charge-transfer interaction between NiPc and ZnFPc was detected. The origin of such unusual ferromagnetism is understood with the help of Goodenough−Kanamori−Anderson (GKA) empirical rules and the Zener model of sp−d exchange interaction.

Square‐Planar PtII versus Octahedral PtIV Halido Complexes: 195Pt NMR Explained by a Simple Empirical Approach

“…195 Pt NMR spectrum in D 2 O of the square-planar anionic complex [PtI 4 ] 2-, synthesized by the method of Dhara. [59] by previously reported methods [39,59] and exhibited 195 Pt NMR peaks (see Figures S2-S7) at NMR frequencies that fit well the calibration line reported in Figure S1.…”

“…3 by the addition of DCl) after saturation with excess KI, following the procedure previously reported by Dhara. [59] The 195 Pt NMR spectrum of the so formed [PtI 4 ] 2complex anion shows a peak at δ = -5475 ppm, as shown in Figure 3.…”

“…We first prepared the K 2 [PtI 4 ] complex by the method previously reported by Dhara [59] and measured for the first time its 195 Pt NMR chemical shift at δ = -5475 ppm ( Table 1 and Figure 3). This 195 Pt NMR chemical shift value completed the series of known 195 Pt NMR frequencies [31,39] for [PtX 4 ] 2complex anions (X = Cl, Br, I).…”

“…In a typical reaction, the square-planar [PtI n Br 4-n ] 2-(1 ≤ n ≤ 3) anionic complexes were formed in water solution by variants of previously reported procedures. [39,59] In particular, K 2 Figure S1). In analogy with previously reported trans-and cis-[PtCl 2 Br 2 ] 2complexes, [39] the [PtI 2 Br 2 ] 2anions also show two NMR signals corresponding to the presence of two trans and cis isomers with similar 195 Pt NMR signals at δ = -3977 and -3985 ppm, respectively (see Figure S3 and Table 1).…”

“…In a typical reaction, the square-planar [PtI n Cl 4-n ] 2-(1 ≤ n ≤ 3) anionic complexes were formed in water solution by variants of previously reported procedures. [39,59] Figure S1. In contrast to the previously reported [39] trans-and cis-[PtCl 2 Br 2 ] 2and trans-and cis-[PtBr 2 I 2 ] 2complexes described above, only one 195 Pt NMR signal was observed for the [PtI 2 Cl 2 ] 2system at δ = -2103 ppm ( Figure S6 and Table 1).…”