Structural Criteria for the Rational Design of Selective Ligands:  Convergent Hydrogen Bonding Sites for the Nitrate Anion

Abstract

A large number of crystal structures are analyzed to characterize the structural aspects of hydrogen bonding interactions with the NO(3)(-) anion. Further insight is provided by the use of electronic structure calculations to determine stable geometries and interaction energies for NO(3)(-) complexes with several simple hydrogen bond donor groups, including water, methanol, N-methylform-amide, and methane. The results establish the existence of a clear set of structural criteria for the rational design of molecular receptors that complex the NO(3)(-) anion through hydrogen bonding interactions.

“Directed” Assembly of Metallacalix[n]arenes with Pyrimidine Nucleobase Ligands of Low Symmetry: Metallacalix[n]arene Derivatives ofcis‐[a2M(cytosine‐N3)2]2+(M=PtII, PdII;n=4 and 6)

“…[19] Pairs of cations of 6 of identical chirality trap two different nitrate anions, acting as a host for nitrates through directional hydrogen bonding (see the Supporting Information). [21] The cytosinate ligands present in 6 are special in that they formally represent a rare tautomeric form (Scheme 1), stabilized by twofold metal coordination through N3 and N4. Although cytosine deprotonates at N1 with a pK a of~12.15, [22] the cytosine anion present in 6 has lost a proton from the exocyclic amino group while still maintaining the proton at N1.…”

Two Chloride Ions as a Template in the Formation of a Cyclic Hexaurea

“…The cyclic arrangement of three urea subunits should be advantageous for planar anions with C 3 symmetry, such as nitrate or carbonate. [6] Computer simulations suggested that the linkage of such anions by three rigid structural elements of the xanthene type would be very promising. Since receptor properties in general are determined by a delicate balance between the prearrangement of ligating functions ("rigidity") and the ability to adapt to the target guest ("flexibility") we decided to partly replace the xanthene units by the more flexible diphenyl ether unit.…”

Ion‐Pair Recognition by Ditopic Macrocyclic Receptors

“…Hay calculates that the preference for hydrogen bonding to the oxygen lone pairs over the π-electron density is about 2 kcal/mol. [31] Shown in Figures 5-7 are three X-ray structures of receptor 13 complexed with NaNO 3 , KNO 3 , or LiNO 3 .…”