Novel Routes to Cu(salicylaldimine) Covalently Bound to Silica: Combined Pulse EPR and in Situ Attenuated Total Reflection-IR Studies of the Immobilization
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- 作者：Eamonn F. Murphy ; Davide Ferri ; Alfons Baiker ; Sabine Van Doorslaer ; and Arthur Schweiger
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：April 21, 2003
- 年：2003
- 卷：42
- 期：8
- 页码：2559 - 2571
- 全文大小：226K
- 年卷期：v.42,no.8(April 21, 2003)
- ISSN：1520-510X
文摘
Several novel routes for the immobilization of modified Cu(salicylaldimine) complexes on commercially availablesilica are described. New pulse electron paramagnetic resonance (EPR) and electron-nuclear double resonancesequences, which provide more detailed information than that available previously, in combination with continuouswave EPR, allow a definitive assignment of the geometry at the copper center in the immobilized Cu(salicylaldimine).Immobilization of the modified Cu(salicylaldimine) on silica was followed in situ by monitoring the intensity of thecharacteristic free- and metal-coordinated imine bands as a function of time using attenuated total reflectance IRspectroscopy. On the basis of these studies, the outcome of the Schiff base condensation of Cu-bis(salicylaldehyde)with 
-aminopropyl-modified silica gel is shown to provide immobilized trans-O2N2- and O3N-coordinated immobilizedCu(salicylaldimine)-type compounds. In addition, trans-O2N2- or O3N-coordinated copper centers are selectivelyprepared on silica by controlling the aminopropyl modifier loading, thus opening a route to compounds not availableby conventional synthesis. The O3N-coordinated Cu(salicylaldimine)-type compound on silica was investigated asa precursor for the synthesis of a tethered chiral Cu(salicylaldimine) via reaction of the coordinated carbonyl groupwith (R)-(+)-
-methylbenzylamine. Supported Cu(salicylaldimine) was also prepared via the immobilization of theappropriate silylethoxy-modified homogeneous precursor on silica gel. Precursors and silica-supported Cu(salicylaldimine) materials have been fully characterized. Comparisons are drawn with related Cu(salicylaldimine) immobilizedin silica aerogels.
-aminopropyl-modified silica gel is shown to provide immobilized trans-O2N2- and O3N-coordinated immobilizedCu(salicylaldimine)-type compounds. In addition, trans-O2N2- or O3N-coordinated copper centers are selectivelyprepared on silica by controlling the aminopropyl modifier loading, thus opening a route to compounds not availableby conventional synthesis. The O3N-coordinated Cu(salicylaldimine)-type compound on silica was investigated asa precursor for the synthesis of a tethered chiral Cu(salicylaldimine) via reaction of the coordinated carbonyl groupwith (R)-(+)--methylbenzylamine. Supported Cu(salicylaldimine) was also prepared via the immobilization of theappropriate silylethoxy-modified homogeneous precursor on silica gel. Precursors and silica-supported Cu(salicylaldimine) materials have been fully characterized. Comparisons are drawn with related Cu(salicylaldimine) immobilizedin silica aerogels.