UncleAl Posted May 26, 2005 Report Share Posted May 26, 2005 Chemists play with symmetries. Identical-radius spheres densely pack. An octahedrally coordinated metal ion is mostly spherical. Symmetric bidentate chelate ligands give chiral point group C3 three-bladed propeller molecules, with a /_-(delta) right hand screw or a /-(lambda) left hand screw. Do identical radius homochiral cations and anions give a chiral cubic lattice with only rotational symmetries? Inorg. Syn. 6 186 (1960){Co(en)3}(3+)en = 1,2-diaminoethane Inorg. Syn. 8 204 (1966){Co(ox)3}(3-)ox = oxalate dianion Both complex ions occur as fully resolved optical isomers. Will the homochiral 1:1 salt be FCC/CCP close packed? Will the unit cell have its axes tilted out of cubic? Will the macroscopic crystal have interesting optical properties? http://www.mazepath.com/uncleal/trisco.png Trivalent ions of identical size build a strongly bonded lattice. It's a nice science project. Turtle 1 Quote Link to comment Share on other sites More sharing options...
Turtle Posted May 27, 2005 Report Share Posted May 27, 2005 ___I'm no chemist, but I have an intimate knowledge of aspects of symmetry. Offhand, I recall 2 different arrangements for close packing identical spheres; one has the spheres in a "box" arrangement with alligned columns & rows & the other the spheres are nested. I don't have my references at hand as I'm in the middle of a move, but I seem to recall in the symmetrey of nested spheres the ratio of sphere volume to interspaces volume is 6 to 1. ___Neither do I have at hand the mathematical expression for counting the succesive layers of close packed spheres, but somewhere I have subjected the elements generated by that expression to my Katabatak analysis (reference thread "Katabatak Math..." for more on Katabataks).___I hope I have contributed something here, or at least not detracted. :naughty: :hihi: Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.