Monday, September 20, 2010
On the pitch angle of a beaded EMAC
I figured out a simple method to estimate the pitch angle of a beaded EMAC that consists of two types of beads, say with diameter a and b (a>b). Beads with size a are used to mimic metal-metal bonds and beads with size b are used to mimic bonds of surrounding ligands. The pitch angle θ can be shown to be approximately given by cosθ=a/(sqrt(3)b) or θ=cos-1(a/sqrt(3)b). Thus if one use 8mm and 6mm beads to make a bead model of the EMAC compound, the pitch angle can be shown to be θ=cos-1(8/sqrt(3)*6)= 30. By inspection, one can see that this angle is quite close to that in the beaded model Chuang made. The angle is a little larger than the experimental observation, though.