Multifunctional Magnetic Molecular {[MnII(urea)2(H2O)]2[NbIV(CN)8]}n System: Magnetization-Induced SHG in the Chiral Polymo

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• 作者：Dawid Pinkowicz ; Robert Podgajny ; Wojciech Nitek ; Micha艂 Rams ; Anna Ma艂gorzata Majcher ; Tomohiro Nuida ; Shin-ichi Ohkoshi ; Barbara Sieklucka
• 刊名：Chemistry of Materials
• 出版年：2011
• 出版时间：January 11, 2011
• 年：2011
• 卷：23
• 期：1
• 页码：21-31
• 全文大小：1164K
• 年卷期：v.23,no.1(January 11, 2011)
• ISSN：1520-5002

文摘

Incorporation of urea molecules into the magnetic system Mn^II-[Nb^IV(CN)₈] results in formation of two magnetic polymorphs {[Mn^II(H₂O)(urea)₂]₂[Nb^IV(CN)₈]}_n chiral 伪 and centric 尾 crystallizing in space groups P4₁ and P1̅, respectively. Both polymorphs exhibit extremely similar structures and are soft ferrimagnets with critical temperatures of 43 and 42 K, respectively. The presence of coordinated urea in the noncentrosymmetric 伪 produces NLO functionality, second harmonic generation (SHG), whereas centric 尾 is just another molecular magnet. As a result of interaction of both functionalities below magnetic ordering temperature, the magnetization-induced SHG (MSHG) is observed for polymorph 伪. The observed MSHG/SHG signal ratio was the largest among molecule-based noncentrosymmetric magnets. The presence of urea molecules in both polymorphs gives also rise to their interesting topotactic reactivity. Both polymorphs can be easily transformed into a new entity {[Mn^II(H₂O)]₂[Nb^IV(CN)₈]路2.5MeOH}_n 2b with significant shift of critical temperature T_c to 70 K. Subsequent hydration of 2b leads to {[Mn^II(H₂O)₂]₂[Nb^IV(CN)₈]路4H₂O}_n 3 with T_c of 47 K.