Polyfunctional inorganic-organic hybrid materials: an unusual kind of NLO active layered mixed metal oxalates with tunable magnetic properties and very large second harmonic generation.
Mixed M(II)/M(III) metal oxalates, as "stripes" connected through strong hydrogen bonding by para-dimethylaminobenzaldeide (DAMBA) and water, form an organic-inorganic 2D network that enables segregation in layers of the cationic organic NLO-phore trans-4-(4-dimethylaminostyryl)-1-methylpyridinium, [DAMS+]. The crystalline hybrid materials obtained have the general formula [DAMS]4[M2M'(C2O4)6].2DAMBA.2H2O (M = Rh, Fe, Cr; M' = Mn, Zn), and their overall three-dimensional packing is non-centrosymmetric and polar, therefore suitable for second harmonic generation (SHG). All the compounds investigated are characterized by an exceptional SHG activity, due both to the large molecular quadratic hyperpolarizability of [DAMS+] and to the efficiency of the crystalline network which organizes [DAMS+] into head-to-tail arranged J-type aggregates. The tunability of the pairs of metal ions allows exploiting also the magnetic functionality of the materials. Examples containing antiferro-, ferro-, and ferri-magnetic interactions (mediated by oxalato bridges) are obtained by coupling proper M(III) ions (Fe, Cr, Rh) with M(II) (Mn, Zn). This shed light on the role of weak next-nearest-neighbor interactions and main nearest-neighbor couplings along "stripes" of mixed M(II)/M(III) metal oxalates of the organic-inorganic 2D network, thus suggesting that these hybrid materials may display isotropic 1D magnetic properties along the mixed M(II)/M(III) metal oxalates "stripes".
Cariati
Elena
E
Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Università di Milano, Centro CIMAINA, UdR di Milano INSTM and Centro ISTM-CNR, Via Venezian 21, Milano, Italy. elena.cariati@unimi.it
Macchi
Roberto
R
Roberto
Dominique
D
Ugo
Renato
R
Galli
Simona
S
Casati
Nicola
N
Macchi
Piero
P
Sironi
Angelo
A
Bogani
Lapo
L
Caneschi
Andrea
A
Gatteschi
Dante
D