This journal is c The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011 New J. Chem., 2011, 35, 2089–2094 2089 Cite this: New J. Chem., 2011, 35, 2089–2094 High quality nano-patterned thin films of the coordination compound {Fe(pyrazine)[Pt(CN) 4 ]} deposited layer-by-layerwz Carlos Bartual-Murgui, a Lionel Salmon, a Amal Akou, a Christophe Thibault, b Ga´bor Molna´r, a Tarik Mahfoud, ac Zouheir Sekkat, cd Jose´ Antonio Real e and Azzedine Bousseksou* a Received (in Montpellier, France) 7th March 2011, Accepted 15th April 2011 DOI: 10.1039/c1nj20212j An optimised procedure was developed for the layer-by-layer deposition of the Hofmann clathrate-like coordination compound {Fe(pyrazine)[Pt(CN) 4 ]} either as continuous or as nano-patterned thin films. Characterization of the thickness and topography of the thin films by atomic force microscopy (AFM) and by surface plasmon resonance (SPR) spectroscopy, which also yields the layer’s refractive index and losses, are reported. We found that the films are of good optical quality and the results of both AFM and SPR experiments are in good agreement with the theoretical predictions of the films thicknesses. Introduction The phenomenon of spin crossover (SCO) between high-spin (HS) and low-spin (LS) states of 3d 4 –3d 7 transition metal ion complexes has been extensively investigated at the molecular level as well as in the solid state. 1 These complexes can change their optical, magnetic and electrical properties upon various external stimuli such as temperature, pressure, magnetic field or light irradiation. Although the origin of the spin crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly determined by short- and long-range interactions (of mainly elastic origin) between the transition metal ions, giving rise to remarkable cooperative phenomena, such as first-order phase transitions accompanied by a hysteresis effect. One of the most interesting open questions in this research field concerns the effect of size reduction on the cooperativity and on the relevant physical properties. 2–15 Notably, the hysteresis, which accompanies in certain cases the thermal spin transition, is considered as an important property as it confers a memory effect on these systems. Two distinct strategies have been developed for the synthesis of SCO materials at the micro- and nanometric scale: the fabrication of spin crossover nanoparticles using various micro- and nano-reactors 2–10 and lithography-assisted deposition methods to obtain micro- and nano-patterned films. 11–15 In our group, we have developed a method for the fabrication of nano-patterned thin films of the family of three- dimensional Hofmann clathrate-like SCO coordination complexes {Fe(L)[M(CN) 4 ]} (L = pyrazine or azopyridine, M = Ni, Pd or Pt) using electron-beam lithography and a sequential assembly method. 11–13 These thin films (either continuous or patterned) exhibited interesting temperature and light-induced spin crossover properties as well as host–guest phenomena. Beside their fundamental interest, these films have also appealing technological perspectives for nano-electronic and nano-photonic devices. However, the control of the quality of the film thickness and roughness is still a challenging objective. As it was highlighted in a recent review by Zacher et al. 16 such metal–organic framework materials are insoluble in any solvent without decomposition and it is not straightforward to deposit them as homogeneous and well-defined crystalline layers on a given substrate for subsequent integration into any functional devices. In this paper, we report an optimised procedure for the elaboration of high quality thin films of the Hoffmann clathrate-like 3D network {Fe(pyrazine)[Pt(CN) 4 ]}. The continuous and nano-patterned films were characterized by atomic force microscopy (AFM) and surface plasmon reso- nance spectroscopy in order to evaluate the film morphology (thickness and roughness) as well as to determine the complex refractive index of the layers. a LCC, CNRS & Universite ´ de Toulouse (UPS, INP), 205 route de Narbonne, F-31077 Toulouse, France. E-mail: azzedine.bousseksou@lcc-toulouse.fr b LAAS, CNRS & Universite ´ de Toulouse (UPS, INSA, ISAE), 7 avenue du Colonel Roche, F-31077 Toulouse, France c Optics & Photonics Center (OPC), Moroccan Foundation for Science, Innovation and Research (MAScIR), Technopolis Rabatshore, Morocco d Hassan II Academy of Science and Technology, Rabat, Morocco e Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, C/Catedra ´tico Jose ´ Beltra ´n Martı´nez, 2, 46980 Paterna, Valencia, Spain w This article is part of a themed issue dedicated to Professor Didier Astruc. z Electronic supplementary information (ESI) available: Additional AFM images. See DOI: 10.1039/c1nj20212j NJC Dynamic Article Links www.rsc.org/njc PAPER Published on 26 May 2011. Downloaded by CEA VALRHO on 10/12/2013 07:32:48. View Article Online / Journal Homepage / Table of Contents for this issue