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 Elena Cariati,* ,² Roberto Macchi, ² Dominique Roberto, ² Renato Ugo, ² Simona Galli, ‡ Nicola Casati, § Piero Macchi,* ,§ Angelo Sironi, § Lapo Bogani, | Andrea Caneschi, | and Dante Gatteschi* ,| Contribution from the Dipartimento di Chimica Inorganica, Metallorganica e Analitica, UniVersita ` di Milano, Centro CIMAINA, UdR di Milano INSTM and Centro ISTM-CNR, Via Venezian 21, 20133Milano, Italy, Dipartimento di Scienze Chimiche e Ambientali, UniVersita ` dell’Insubria, Via Valleggio 11, 22100 Como, Italy, Dipartimento di Chimica Strutturale e Stereochimica Inorganica and Centro ISTM-CNR, Via Venezian 21, 20133 Milano Italy, and Dipartimento di Chimica UniVersita ` di Firenze and UdR di Firenze INSTM, Via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy Received February 21, 2007; Revised Manuscript Received May 28, 2007; E-mail: elena.cariati@unimi.it; piero.macchi@unimi.it; dante.gatteschi@unifi.it Abstract: 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”. Introduction In the past few years, inorganic-organic hybrid crystalline materials with interesting electrical, magnetic, and nonlinear optical (NLO) properties have attracted the attention of the material science community, 1 in particular the appealing poly- functional hybrids. 2 The macroscopic functionalities of the latter can be originated by the combination of each individual component properties or by cooperative effects produced by a specific structural assembling. The advantage of resorting, at least in part, to molecular species of known properties prompts us to rationalize the engineering of the final material, thus allowing a tunability of the desired properties. In fact, the main purpose of the current research is to find the proper synergy between the two subsystems (organic and inorganic), each of which should contribute to retain (if not enhance) the other’s property in an extended crystalline framework. Within this wide new field, the coupling of magnetic and nonlinear optical properties is quite attractive 3 but yet largely unexplored. In particular, applications of combined electro-optic and magnetic materials have not received adequate attention, so far. In hybrid materials, the most usual provider of the magnetic properties is the inorganic part, whereas significant second-order NLO responses are more frequently originated from the organic ² Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Universita ` di Milano. ‡ Universita ` dell’Insubria. § Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita ` di Milano. | Dipartimento di Chimica Universita ` di Firenze. (1) Knutson, J. L.; Martin, D. J.; Mitzi, D. B. Inorg. Chem. 2005, 44, 4699. Rabu, P.; Drillon, M. AdV. Eng. Mat. 2003, 5, 189. Coe, B. J.; Curati, N. R. Comments Inorg. Chem. 2004, 25, 147. (2) See, for example: Functional Hybris Materials; Gomez-Romero, P., Sanchez, C., Eds.; Wiley-VCH Verlag GmbH & Co. KgaA: Weinheim, Germany, 2004. (3) (a) Lacroix, P. G. Chem. Mater. 2001, 13, 3495. (b) Coronado, E.; Gala ´n- Mascaro ´s, J. R.; Romero, F. In Functional Hybris Materials; Gomez- Romero, P., Sanchez, C., Eds.; Wiley-VCH Verlag GmbH & Co. KgaA: Weinheim, Germany, 2004. Published on Web 07/07/2007 9410 9 J. AM. CHEM. SOC. 2007, 129, 9410-9420 10.1021/ja0710712 CCC: $37.00 © 2007 American Chemical Society