Structure and NLO Properties of Layered Bimetallic Oxalato-Bridged Ferromagnetic Networks Containing Stilbazolium-Shaped Chromophores

Abstract

A series of 35 layered compounds A[M II Cr III (C 2 O 4 ) 3 ]‚n solvent has been synthesized with five different metals (M ) Mn, Fe, Co, Ni, Cu) and seven hyperpolarizable stilbazolium-shaped A chromophores: (4-[4-(dimethylamino)-R-styryl]-N-alkylpyridinium), alkyl ) methyl, ethyl, isopropyl (DAMS, DAES, DAPS respectively); (4-[4-methoxy-R-styryl]-N-alkylpyridinium), alkyl ) isopentyl, heptyl (MIPS, MHS); DAZOP and CINDAMS are DAMS analogues, where the central [CdC] core has replaced by azo or butadiene cores, respectively)]. These compounds have been designed as possible multiproperty materials associating ferromagnetism and second-order optical nonlinearity. Two-third of these compounds exhibit second harmonic generation (with efficiency up to 100 times that of urea at 1.9 µm), the others being inactive. All of them order ferromagnetically below Curie temperatures that range from 6 to 13 K. The structures of DAPS[Mn II -Cr III (C 2 O 4 ) 3 ].CH 3 CN and MIPS[Mn II Cr III (C 2 O 4 ) 3 ] have been resolved. Both of them belong to the centrosymmetric P2 1 /c space group, which accounts for their NLO inactivity. The long axes of the chromophores in a given layer are parallel, but the dipolar moments are antiparallel. Two successive chromophore layers along the stacking direction have approximately orthogonal orientations, giving rise to a doubling of the c parameter. X-ray powder diffraction shows that the high crystalline compounds of the series possess the same monoclinic unit cell as A[Mn II Cr III (C 2 O 4 ) 3 ] (A ) DAPS, MIPS). A search for structure-property correlation emphasizes the relationship between a short interlayer distance and the alignment of the chromophore dipoles.

Recent Advances on Anilato-Based Molecular Materials with Magnetic and/or Conducting Properties

“…Similar cation- The tetrabutylammonium countercations are crucial for templating the 3D structure, compared with other 1D or 2D hydranilate-based materials [7,108,125,[186][187][188] since were located inside the pores and appear to fill the pores almost completely with no large voids present. Similar cation-dependent morphology changes have been observed for transition metal-oxalate coordination compounds with analogous chemical formula [A + ] 2 M II 2 (ox) 3 [72,81,[189][190][191]. The electronic absorption spectrum broad absorbance extending across the range 4500-14,000 cm −1 , with ν max = 7000 cm −1 .…”

“…(NBu4)2Fe III 2(H2An)3 (43) shows a very rare topology for H2An 2− -based coordination compounds [81,112,121,125], with two interpenetrated (10,3)-a lattices of opposing chiralities where neighboring metal centers within each lattice are all of the same chirality (Figure 30b,c), generating a threedimensional structure (Figure 30a-d). This topology differs from the classic 2D honeycomb structure type frequently observed for hydranilates and derivatives, where neighboring metal centers are of opposing chiralities [108,125].…”

“…44 shows a lower conductivity of 0.0062(1) S/cm at 298 K and a considerably larger activation energy of 180 meV which is consistent with a further divergence of the H 2 An 3− /H 2 An 2− ligand ratio from the optimal mixed-valence ratio of 1:1 ( Figure 31). [72,81,[189][190][191]. The electronic absorption spectrum broad absorbance extending across the range 4500-14,000 cm −1 , with νmax = 7000 cm −1 .…”

“…In the last 20 years many efforts have been addressed to add in these materials a further physical property by playing with the functionality of the A + cations located between the bimetallic layers. This strategy produced a large series of multifunctional molecular materials where the magnetic ordering of the bimetallic layers coexists or even interacts with other properties arising from the cationic layers, such as paramagnetism [2,[76][77][78][79][80], non-linear optical properties [2,81,82], metal-like conductivity [83,84], photochromism [2,81,85,86], photoisomerism [87], spin crossover [88][89][90][91][92][93], chirality [94][95][96][97], or proton conductivity [2,98,99]. Moreover, it is well-established that the ordering temperatures of these layered magnets are not sensitive to the separation determined by the cations incorporated between the layers, which slightly affects the magnetic properties of the resulting hybrid material, by emphasizing its 2D magnetic character [2,[75][76][77][78][79][80]95,100,101].…”

Weak ferromagnetism with very large canting in a chiral lattice:Fe(pyrimidine)2Cl2Feyerherm1, Loose2, Ishida3 et al. 2004Phys. Rev. B410220View full textAdd to dashboardCite

“…7 In this framework, extensive efforts are undertaken to find chiral magnetic materials that exhibit magnetochiral dichroism (MChD), a phenomenon first observed by Rikken and Raupach in a chiral paramagnetic material. 8 Large MChD is expected in materials that combine chirality and magnetic order.…”