Molecular engineering to control the magnetic interaction between single-chain magnets assembled in a two-dimensional network.

Two two-dimensional (2D) systems having the formula [{Fe(III)(dmbpy)(CN)(4)}(2)Co(II)L](n) [L = pyetNO (1), tvpNO (2)] and consisting of single-chain magnets connected through organic ligands (L) have been prepared, and their magnetic properties have been investigated. The overall magnetic behavior depends on the capacity of the organic pillars to transmit long-range magnetic interactions. 1 is the first example of a 2D compound exhibiting double relaxation of the magnetization, whereas 2 behaves as a metamagnet.

Prussian blue analogues of reduced dimensionality.

Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule-based materials can combine physical and chemical properties associated with molecular-scale building blocks, their successful integration into real devices depends primarily on higher-order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced-dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is built up by means of a modified Langmuir-Blodgett technique, where the PBA is synthesized from precursors in a self-limited reaction on a clay mineral surface. The focus of this work is understanding the magnetic properties of the PBAs in different periodic, low-dimensional arrangements, and the influence of the "on surface" synthesis on the final properties and dimensionality of the system.

The molecularly controlled synthesis of ordered bi-dimensional C60 arrays.

Much of the research effort concerning the nanoscopic properties of clays has focused on its mechanical applications, for example, as nanofillers for polymer reinforcement. To broaden the horizon of what is possible by exploiting the richness of clays in nanoscience, herein we report a bottom-up approach for the production of hybrid materials in which clays act as the structure-directing interface and reaction media. This new method, which combines self-assembly with the Langmuir-Schaefer technique, uses the clay nanosheets as a template for the grafting of C(60) into a bi-dimensional array, and allows for perfect layer-by-layer growth with control at the molecular level. In contrast to the more-common growth of C(60) arrays through nanopatterning, our approach can be performed under atmospheric conditions, can be upscaled to areas of tenths of cm(2), and can be applied to almost any hydrophobic substrate. Herein, we report a detailed study of this approach by using temperature-dependent X-ray diffraction, spectroscopic measurements, and STM.

A Langmuir-Schaefer approach for the synthesis of highly ordered organoclay thin films.

The Langmuir-Schaefer (LS) method has been investigated as a means to control the structure of hybrid organoclay thin films consisting of montmorillonite and dimethyldioctadecylammonium (DODA) cations. We observed a significant modification of the compression isotherms as a function of clay mineral concentration in the subphase, implying clay interaction with the alkylammonium monolayer. For a particular range of clay concentrations, LS hybrid monolayers could be readily prepared on a hydrophobic substrate. The structure of hybrid multilayers of DODA and clay platelets, prepared by repeated LS deposition, was found to be governed by the synthetic route: when the multilayer is fabricated by transferring the hybrid Langmuir films from the surface of the clay dispersion, the DODA-clay particles "flip over" while passing through the meniscus during the even cycles of the deposition, as demonstrated from the elemental analysis of the surface by X-ray photoelectron spectroscopy. In our new model for these multilayers, the structural building block consists therefore of two interdigited DODA layers and two clay layers held together by Na(+). Additionally, a minority phase forms, probably differing from the majority one in the conformation of the alkylammonium cations, and can be eliminated by annealing. This deposition procedure leads to a less ordered structure than an alternative route which combines LS deposition and self-assembly to produce a multilayer consisting of two interdigited DODA layers and one clay layer: here the hydrophilic surface of the transferred hybrid Langmuir film is converted to a hydrophobic surface by dipping into a solution of DODA cations before proceeding with the LS deposition of the next layer.