In the previous post
I pondered the colour of Monastral blue (copper phthalocyanine). Something did not quite fit, and so I speculated that perhaps some oxidation of the pigment might give a new species. This species (Cambridge code FEGJOQ) comprises two parts of copper phthalocyanine, 1 part of the corresponding cation, and 1 part of triodide anion. Looking at the packing of this system, I spotted something I had seen some time ago in NaI2.Acetone, namely an infinitely long and absolutely straight chain of iodine atoms, a molecular wire if you like.
An iodine molecular wire.
A different view shows how this wire runs down layers of the phthalocyanine. The iodines are 3.2Å apart, compared to the sum of their van der Waals radii of ~4.0Å.
FEGJOQ, seen edge on. Click for 3D
End on view, showing the filling of the channel by iodines. Click for 3D
Tags: Cambridge, molecular wire, phthalocyanine
The original authors of the paper reporting this structure do not agree with your analysis of the iodines. Their 1987 JACS paper (DOI: 10.1021/ja00238a021
) refers back to the isomorphous Ni species that they reported in an earlier 1980 JACS paper (DOI: 10.1021/ja00542a008
). In this earlier paper they include a detailed analysis of the iodines (pages 6708 and 6709) and conclude that they have disordered chains of linked (I3)- anions. So, no continuous iodine wire, I’m afraid.
It boils down to whether linked chains of I3- are continuous or not, the key operator being linked. Another interesting question is whether the oscillation in bond length is a Peierls distortion or not.