A heterocyclic metal ring contains metal-metal bonds that connect
adjacent metal atoms of the ring structure. Such rings may also be
considered as polynuclear complexes in which each metal atom
is bound to its two nearest ring neighbors, but not to all other
metal atoms of the ring (as in small metal clusters).
In most cases, neither the metal-metal bonds nor the bonds
between metal atoms and atoms of possible ligands are adequately
represented by SMILES bond symbols. The CurlySMILES language
overcomes this problem by providing the unspecified-bond
symbol ~ as well as a format
to include ligands and assign interactions between
ligand-atoms and nuclei. The following example shows the
notation for a six-membered heavy-atom heterocycle:
The four metal atoms and the two antimony atoms are
coordinated with ligands. This is indicated via the annotation
{+L}, without including details.
This notation serves as a template to encode the heterocycle
[Re2(CO)8(μ-SbPh2)(μ-H)]2
(Ph = phenyl),
which is shown below and has been prepared by palladium-catalyzed
ring-opening cyclodimerization of the three-membered heterocycle
Re(CO)8(μ-SbPh2)(μ-H) [2,3].
Its notation is derived by filling the notations for the
carbonyl, phenyl and μ-H ligands into the template:
A. Drefahl:
CurlySMILES: a chemical language
to customize and annotate encodings of molecular and
nanodevice structures.
J. Cheminf.2011, 3:1;
doi:
10.1186/1758-2946-3-1
.
[2]
R. D. Adams, W. C. Pearl, Jr.
Y. O. Wong, Q. Zhang, M. B. Hall and J. R. Walensky:
Tetrarhena-heterocycle from the
Palladium-Catalyzed Dimerization of
Re2(CO)8(μ-SbPh2)(μ-H)
Exhibits an Unusual Host-Guest Behavior.
J. Am. Chem. Soc.2011,
133
(33),
12994-12997.
doi:
10.1021/ja205515u
.
[3]
S. Ritter:
Heavy-Metal Ring Bags Metal Atom
.
Chem. & Eng. News2011,
89
(32),
13.