Insect Control: Biological and Synthetic Agents - Index of

74 3: Neonicotinoid Insecticides
Figure 11 Isosurfaces for Fukui functions for nucleophilic attack of (a) imidacloprid, (b) clothianidin, (c) dinotefuran, and
(d) acetamiprid. Three levels of isosurfaces are displayed: 0.005 (green, opaque), 0.001 (yellow, transparent), and 0.0005 (white,
transparent).
Figure 12 Isosteric alternatives to the heterocyclic N-substituents. Connolly surfaces of the CPM moiety from imidacloprid,
nitenpyram, acetamiprid (blue), CTM moiety from thiamethoxam and clothianidin (magenta), and TFM from ( )-dinotefuran (green).
Atomic charges have been driven via the Mulliken partitioning scheme DFT/BP/TZVP/COSMO Kohn–Sham orbitals. (a) H-bonding
potentials is mapped onto the Connolly surface; (b) atomic charges are projected onto the Connolly surface. (Reproduced with
permission from Jeschke, P., Schindler, M., Beck, M., 2002. Neonicotinoid insecticides: retrospective consideration and prospects.
Proc. BCPC: Pests and Diseases 1, 137–144.)
procedures are helpful to predict the receptor–ligand
interaction (Nakayama, 1998; Okazawa et al., 1998,
2000).
As described in an alternative binding model for
imidacloprid, the interatomic distance of 5.9 A ˚
between the oxygen of the nitro group (at the van
der Waals surface) and the nitrogen in 1-position
was also noted as adequate (Kagabu, 1997a). That
means the oxygen of the nitro group and the cyano
nitrogen are well suited as acceptors for hydrogen
bonding with the nAChR, in place of ring nitrogen
atoms in CPM and CTM or the ring oxygen in
TFM. Thus the p-conjugated system composed of a
N-nitroimino or N-cyanoimino group and the conjugated
nitrogen in 1-position are considered essential
moieties for the binding of neonicotinoids
to the putative cationic subsite in insect nAChR
(Figure 13). On the other hand, Maienfisch et al.