A chiral molecular wire.

More than 60 million molecules are known, and many are fascinating. But beauty is in the eye of the beholder. Thus it was that I came across the attached molecule[1]. It struck me immediately as, well, beautiful!

This is one that comes to life in 3D and I strongly urge you to inspect it as such by clicking on the above. Why is it so interesting? Well, it has as its backbone a linear array of seven Nickel atoms. The Ni…Ni distances are around 2.2-2.3Å, and this “wire” is wrapped with a square planar arrangement of nitrogen atoms deriving from the ligand.

But that is not just where I perceived its beauty. The molecule has D₄ symmetry, and is therefore dissymetric (chiral). The ligands wrap themselves around the metal wire in a helical arrangement. Oddly, the original authors who reported this lovely molecule make little (nothing?) of this aspect. Can it be resolved for example? Can it recognise other chiral molecules? What are its chiroptical properties (optical rotation, circular dichroism spectra etc)? Anyway enough from me; just go and enjoy this gem! 

References

1. S. Lai, T. Lin, Y. Chen, C. Wang, G. Lee, M. Yang, M. Leung, and S. Peng, "Metal String Complexes:  Synthesis and Crystal Structure of [Ni₄(μ₄-phdpda)₄] and [Ni₇(μ₇-teptra)₄Cl₂] (H₂phdpda = N-Phenyldipyridyldiamine and H₃teptra = Tetrapyridyltriamine)", Journal of the American Chemical Society, vol. 121, pp. 250-251, 1998. http://dx.doi.org/10.1021/ja982065w