Slow Relaxation of the Magnetization in Non-Linear Optical Active Layered Mixed Metal Oxalate Chains

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• 作者：Elena Cariati ; Renato Ugo ; Giuseppe Santoro ; Elisa Tordin ; Lorenzo Sorace ; Andrea Caneschi ; Angelo Sironi ; Piero Macchi ; Nicola Casati
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：December 6, 2010
• 年：2010
• 卷：49
• 期：23
• 页码：10894-10901
• 全文大小：931K
• 年卷期：v.49,no.23(December 6, 2010)
• ISSN：1520-510X

文摘

New Co^II members of the family of multifunctional materials of general formula [DAMS]₄[M₂Co(C₂O₄)₆]·2DAMBA·2H₂O (M^III = Rh, Fe, Cr; DAMBA = para-dimethylaminobenzaldehyde and [DAMS⁺] = trans-4-(4-dimethylaminostyryl)-1-methylpyridinium) have been isolated and characterized. Such new hybrid mixed metal oxalates are isostructural with the previously investigated containing Zn^II, Mn^II, and Ni^II. This allows to preserve the exceptional second harmonic generation (SHG) activity, due to both the large molecular quadratic hyperpolarizability of [DAMS⁺] and the efficiency of the crystalline network which organizes [DAMS⁺] into head-to-tail arranged J-type aggregates, and to further tune the magnetic properties. In particular, the magnetic data of the Rh^III derivative demonstrate that high spin octacoordinated Co^II centers behave very similarly to the hexacoordinated Co^II ones, being dominated by a large orbital contribution. The Cr^III derivative is characterized by ferromagnetic Cr^III−Co^II interactions. Most relevantly, the Fe^III compound is characterized by a moderate antiferromagnetic interaction between Fe^III and Co^II, resulting in a ferrimagnetic like structure. Its low temperature dynamic magnetic properties were found to follow a thermally activated behavior (τ₀ = 8.6 × 10⁻¹¹ s and ΔE = 21.4 K) and make this a candidate for the second oxalate-based single chain magnet (SCM) reported up to date, a property which in this case is coupled to the second order non linear optical (NLO) ones.