Novel materials from bis(arene)metal-containing polyacrylonitrile

Abstract

Novel bis(arene)metal-containing polyacrylonitrile materials have been prepared by the polycyanoethylation reaction between acrylonitrile and (arene) 2 M (M = Cr or V; arene = PhH, C 6 H 4 Et 2 or mesitylene) in the absence of solvent. The resulting star-shaped molecules consist of a central (arene) 2 M species with up to four polyacrylonitrile arms covalently bonded to the arene ligands. The materials are readily soluble and films can be cast from solutions in acetonitrile. The IR and solid state 13 C NMR spectra (or EPR spectrum for the oxidized chromium-containing polymer) are consistent with the presence of a metal-arene bond and confirm the persistence of the sandwich structure. The properties of the thermolysed materials are consistent with the formation of conjugated naphthyridine-type structures. The value of |n 2 | determined by the degenerate fourwave mixing technique at 1064 nm with a 6 ns pulse duration for a solution in conc. H 2 SO 4 (1 g l À1 ) of the chromium-containing polymer pyrolysed at 350°C was found to be 0.8 Â 10 À13 cm 2 W À1 corresponding to |Re w (3) | = 0.4 Â 10 À11 esu.There is current interest in soluble polymers containing transition metals because of the requirements for advanced materials in molecular electronics, electro-or magneto-optics and catalytical processes. We expect that polymers containing CN groups and having transition metal sandwich complexes in their macrochains should be promising precursors of organometallic metal-containing nanomaterials with interesting magnetic, optical and perhaps magneto-optical properties following chemical, photochemical or thermal treatment. Miller and co-workers have shown that such materials can be formed by the reaction between bis-benzenevanadium and tetracyanoethylene, which gives rise to a high-temperature ferromagnet. 1,2 Similarly, high temperature ferro-and ferri-magnetic behaviour has been observed for cyanometallate (Prussian blue type) compounds, such as mixed valence chromium cyanides, with excellent photochromic properties. 3 The present report focuses on the synthesis and the characterization of new polymer materials based on polyacrylonitrile incorporating bis(arene)chromium 4 or bis(arene)vanadium compounds chemically bonded into the macrochains.Novel bis(arene)chromium-containing polyacrylonitrile materials have been prepared by the reaction between acrylonitrile and the corresponding bis(arene)chromium complex (or mixture) in the absence of solvent under argon. 4 A cyanoethylation reaction mechanism (Scheme 1) was proposed by Domrachev and Razuvaev to account for APPLIED ORGANOMETALLIC CHEMISTRY

Organometallic self-organized nanomaterials for nonlinear optics

“…The comparison of the spectroscopic characteristics of free PAN after alkaline hydrolysis (Fig 10) and that of Cr+PAN shows a significant increase of the Stokes shift which reaches 4800 cm -1 for Cr + PAN and only 2000 cm -1 for free PAN. It witnesses the presence of intramolecular charge separation in the first excited state of the conjugated system in Cr + PAN, which, in its turn, leads to high χ (3) values for this compound. It can be also an additional indirect piece of evidence of the fact that C=N conjugated chains exist in Cr + PAN not independently but covalently bonded with the sandwich structure.…”

“…[1][2][3][4][5] The resulting star-shaped molecules consist of a central (arene) 2 M species with polyacrylonitrile arms covalently bonded to the arene ligands. The properties of thermolysed bis(arene)metal-containing polyacrylonitrile (MPAN) are consistent with the formation of conjugated ladder-type polynaphthyridine structures.…”

“…The properties of thermolysed bis(arene)metal-containing polyacrylonitrile (MPAN) are consistent with the formation of conjugated ladder-type polynaphthyridine structures. 3,4 Thus, MPAN turns out to be a promising polymer-precursor for the preparation of non-linear optical structures: the value of electronic n 2 determined by the DFWM and Z-scan technique at 1064 nm with a 6 ns pulse duration for a solution in conc. H 2 SO 4 (1 gl -1 ) of the Cr-and V-containing polymers pyrolyzed at 350°C was found to be 0.8 x 10 -13 cm 2 W -1 and 2.2 x 10 -13 cm 2 W -1 , respectively.…”

Chromium-containing organometallic nanomaterials for non-linear optics

“…Previously, we have reported the synthesis of (arene) 2 Mcontaining polyacrylonitrile (M = Cr,V) prepared by the polycyanoethylation reaction between bis-arene complexes and acrylonitrile. [1][2][3][4][5] The resulting star-shaped molecules consist of a central (arene) 2 M species with polyacrylonitrile (PAN) arms covalently bonded to the arene ligands. The properties of thermolysed bis(arene)metal-containing polyacrylonitrile (MPAN) are consistent with the formation of conjugated ladder-type polynaphthyridine structures.…”

“…The properties of thermolysed bis(arene)metal-containing polyacrylonitrile (MPAN) are consistent with the formation of conjugated ladder-type polynaphthyridine structures. 3,4 Thus, MPAN turns out to be a promising polymeric nanocomposite precursor for the preparation of non-linear optical structures: the value of electronic n 2 determined by the DFWM and Z-scan technique at 1064 nm with a 6 ns pulse duration for a solution in concentrated H 2 SO 4 (1 g l À1 ) of the Cr-and V-containing polymers pyrolyzed at 350 1C was found to be 0.8 Â 10 À13 cm 2 W À1 and 2.2 Â 10 À13 cm 2 W À1 , respectively.…”