Zeolite transition metal phthalocyanines

Deoxygenation can be achieved with transition-metal atoms (Ti, V, Cr, Co, Ni) in a high vacuum at low temperature, V and Cr being the most active cis-trans mixtures are obtained with low conversions. The reaction of cyclohexene oxide with transition-metal complexes has been studied on a zeolite matrix of the complexes examined, the copper-phthalocyanine and cobalt-diamine complexes are the most active. 

Other transition metals may be incorporated as carbonyl complexes. Catalytically active complexes of Mn and Fe were prq>ared by synthesizing the complex inside the pores of NaX and NaY zeolites [68,69]. The occluded Mn-bipyridyl and Fe-phthalocyanine complexes catalyze the oxidation of cyciohexene to adipic acid. 

Transition metal complexes of phthalocyanine encaged in faujasite type zeolites have been reported as efficient catalysts in the oxidation of alkanes at room temperature and atmospheric pressure [6-13]. These catalysts constitute potential inorganic mimics of remarkable enzymes such as monooxygenase cytochrome P-450 which displays the ultimate in substrate selectivity. In these enzymes the active site is the metal ion and the protein orientates the incoming substrate relative to the active metal center. Zeolites can be used as host lattices of metal complexes [14, 15]. The cavities of the aluminosilicate framework can replace the protein terciary structure of natural enzymes, thus sieving and orientating the substrate in its approach to the active site. Such catalysts are constructed by the so-called ship in a bottle synthesis the metal phthalocyanine complexes are synthesized in situ within the supercages of the zeolite... 

Various metal complexes such as metal phthalocyanines, metal salenes or Ru pyridyl complexes have been incorporated in molecular sieves such as cavity-structured zeolites (faujasites, supercages with 1.3-nm diameter), channel-structured aluminium phosphates (AIPO4-5, channel diameter 0.73 nm) and channel-structured silicates MCM-41 (channel diameter 3.2 nm) [51-53]. Different strategies were applied for the inclusion of the phthalocyanines. For example, whereas the zeolite-encaged phthalocyanines (1 R = -FI M = Co(II), Ru(II), etc.) are synthesized by the reaction of a transition metal ion-exchanged zeolite with phthalonitrile in a closed-bomb vessel [54], in the cases of AIPO4-5 and MCM-41 substituted derivatives of phthalocyanines were added to the mixture during the hydrothermal synthesis of the molecular sieve [55,56]. 

The in-s rtu synthesis of metalio-phthalocyanines in zeolites can be done via three distinct literature procedures (Scheme 1). The required amount of a given transition metal is brought into the zeolite via a simple ion exchange (procedure A), through adsorption of a TM-carbonyl (B) or a metallocene (C). After removal of the respective TM ligands (water, CO and cyclopentadiene, respectively), 1,2-dicyanobenzene (DCB) is adsorbed onto the TM-zeolite and the mixture heated to form the MePc compiex. Rnally, the sample has to be purified in such a way that oniv occiuded MePc complex remains in the zeolite. The association of DCB with the supercage TM ions in Y zeolite, are schematically shown in Fig. 3. 

Even larger virtual pressure effects (up to about 30 kbar) are observed when bulkier molecules, such as metal phthalocyanines, are synthesized in-situ within zeolite Y cages [3,16]. Fig. 4 represents an encaged Co-phthalocyanine complex within a faujasite framework supercage, experiencing distortions which are reflected in the electronic vibration transitions of the macrocycle. 

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