Sind Metalloprotonencryptanden m¨oglich? – DFT-Studie zur Protonenaffinit¨at von [2.2.2]-analogen Metallocryptanden
Can Metallocryptands act as Proton Cages? – DFT Study of Proton Affinity in [2.2.2]-analogous Metallocryptands
Ralph Puchta und Andreas Scheurer
Anorganische Chemie, Department Chemie und Pharmazie, Universit¨at Erlangen-N¨urnberg, Egerlandstraße 1, 91058 Erlangen, Germany
Reprint requests to Dr. R. Puchta. Fax: (+49) 9131-85-26565. E-mail: ralph.puchta@chemie.uni- erlangen.de or Dr. A. Scheurer. Fax: (+49) 9131-85-27367. E-mail: andreas.scheurer@chemie.uni- erlangen.de
Z. Naturforsch.2010,65b,231 – 237; received December 18, 2009 Herrn Professor Rolf W. Saalfrank zum 70. Geburtstag gewidmet
Based on density functional calculations (RB3LYP/LANL2DZp) the bicyclic metallocryptand [Pd3(L2)2] [(L2)3−: 1,1,1-nitrilotris(5,5-dimethylhexane-2,4-dione trianion)] shows the same high gas-phase basicity (−257.1 kcal mol−1) as Lehn’s [2.2.2] cryptand (−254.4 kcal mol−1). This illus- trates that the concept of metallotopomers adopted by Saalfranket al.can be applied to design proton sponges as well as proton cryptands by metallosupramolecular coordination chemistry. The slightly higher gas-phase proton affinity of [Pd3(L2)2] compared to [2.2.2] can be attributed to the smaller cavity in the metallotopomer.
Key words:Metallocryptand, Cryptand, Proton Sponge, Proton Affinity, DFT Calculations
