Schiff-Base Podates – X-ray, NMR and Ab Initio Molecular-Orbital Studies of the Cadmium(II) Complexes of Linear and Three-Armed Podands in Solution and Solid State
✍ Scribed by Anu Jäntti; Michael Wagner; Michael Wagner; Reijo Suontamo; Erkki Kolehmainen; Kari Rissanen
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 258 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Cadmium(II) complexes of two Schiff bases, 1,3-di(pyridine-spontaneous resolution. Solution studies of 1 in CHCl 3 / DMSO (10:1) and pure DMSO were performed using 1 H-, 2-carboxaldimino)propane (C 15 H 16 N 4 , L1) [1] and tris[4-(2Јpyridyl)-3-aza-3-butenyl]amine (C 24 H 27 N 7 , L2) [2] are 13 C-, 113 Cd-NMR and 1 H, 15 N z-GS HMBC spectroscopy and they suggest a reorientation of 1 into the more symmetrical described. An efficient route utilising molecular sieves for the synthesis of Schiff bases is presented. The ligands L1 and L2 4-coordinate complex due to the flexible nature of L1. The preorganised, potentially tetra-, hexa-or heptadentate, can be described as linear and three-armed podands, respectively, L1 being conformationally flexible and L2 three-armed podand L2 and its in situ complexation with the Cd 2+ cation were investigated by 1 H-, 13 C-, 113 Cd-NMR and preorganised. Cadmium perchlorate in methanol with L1 yields a crystalline complex [Cd(L1) 2 ](ClO 4 ) 2 (1), the 1 H, 15 N z-GS HMBC spectroscopy. The results support the formation of a highly symmetrical helical 6-coordinate structure of which was determined by X-ray structure analysis. The complex 1 has an unusual nonsymmetrical 8-podate [CdL2](NO 3 ) 2 (2). The structure of 2 has also been verified by ab initio HF-MO calculations using a standard 3-coordinated helical structure and crystallizes in an acentric space group (Cc, no. 9) as a pure enantiomer due to 21G* basis set (Lan2DZ for Cd).