Supramolecular Signatures of Adenine-Containing Organostannoxane Assemblies

The
reactions of 3-(N9-adeninyl) propanoic acid (LH) with various di- and
triorganotin oxides have been investigated. Thus, the reaction of di-tert-butyltin oxide (t-Bu2SnO)3 in a 3:1 ratio afforded the dinuclear derivative [t-Bu2Sn­(μ-OH)­L]2·7H2O (1). A similar reaction involving bis­(tri-n-butyltin)­oxide, (n-Bu3Sn)2O, in a 2:1 ratio afforded the one-dimensional (1D) coordination
polymer [n-Bu3SnL·0.33H2O]n (2). Similarly the reaction
with (n-Bu2SnO)n in a 2:1 ratio afforded the tetranuclear [{n-Bu2Sn}2(μ3-O)­(μ-OH)­L]2 (3). On the other hand, a
similar reaction in a 1:1 ratio also gave the tetranuclear product
[{n-Bu2Sn}2(μ3-O)L2]2 (4). The molecular structure
of 1 reveals a central dinuclear Sn2O2 motif where the two tin centers are bridged by two μ-OH
groups. Each tin is bound with a monodentate carboxylate group; the
CO unit of these carboxylates is involved in an intramolecular
hydrogen bonding with the bridging OH unit. The supramolecular structure
of 1 reveals the formation of a 1D zigzag chain mediated
by intermolecular hydrogen bonding interaction through the Watson-Crick
or the Hoogsteen faces. 2 is a 1D coordination polymer
formed by the successive bridging of triorganotin units by the carboxylate
ligand L. The supramolecular structure of 2 reveals that
two 1D coordination polymers interact to generate novel adenine homotrimers
formed as a result of alternating Watson-Crick–Watson-Crick
and Hoogsteen–Watson-Crick interactions. The molecular structures
of 3 and 4 reveal them to be tetranuclear
possessing a ladder-like structure. The essential difference between
their molecular structures is that in 4 there are four
carboxylate ligands, while in 3 there are only two. Both
of these complexes reveal intramolecular and intermolecular hydrogen
bonding and π···π stacking interactions.
The nematicidal activity of 1–3 was
examined against Caenorhabditis elegans. Compound 2 was found to be highly active, effecting a high mortality
even at very low concentrations such as 25 or 10 ppm.