Kumaresh Ghosh

Recognition of insoluble tartaric acid in chloroform

Abstract Simple receptors for the recognition and solubilisation of insoluble tartaric acid in chloroform were designed and synthesised for the first time. Receptors 2 and 3 were successful in solubilising tartaric acid into chloroform forming a 1:1 complex, and were also found to be useful as fluorescent probes for the detection of this substrate.

Molecular recognition: Hydrogen bonding induced configurational locking of a new photoresponsive receptor by dicarboxylic acids

Abstract A new photoresponsive system 1 has been synthesised and recognition by the cavity of the cis -isomer of 1 of dicarboxylic acids of various chain lengths has been studied on irradiation at 310 nm. The cavity of the cis form is found to be selective for adipic acid.

Molecular recognition: Connection and disconnection of hydrogen bonds, a case study with dimeric and highly associated monocarboxylic acids with simple receptors

Abstract The new receptor (5) having mixed diamide moieties is a simple synthetic model which binds carboxylic acids by three point hydrogen bonds involving pyridine nitrogen, pyridine amide as well as the flexible aliphatic amide moieties. This is in contrast to the receptor (6) which makes only two point hydrogen bonds. Binding studies of the simple pyridine amide (3) making two hydrogen bonds with a number of dimeric and highly associated monocarboxylic acids are also reported. Receptor (9) shows higher binding constant with ibuprofen compared to (3).

Anthracene-appended Pyridine Amide: A Simple Sensor for Monocarboxylic Acids

Anthracene-appended receptor 1, which can function as an “on–off” fluorescence switch for monocarboxylic acids, has been designed and synthesized. The photophysical behavior of 1 has been examined by fluorescence, UV–vis and NMR spectroscopy.

2-Aminopyrimidine–terephthalic acid (1:1) complex

Mutual recognition of 2-aminopyrimidine, C 4 H 5 N 3 , and terephthalic acid, C 8 H 6 O 4 , is possible through the formation of cyclic eight-membered hydrogen-bonded rings in the co-crystal. Each molecule can participate in two such hydrogen-bonded ring patterns, and these result in infinite hydrogen-bonded zigzag chains.

Novel Motif of Hydrogen Bonds in the Water-assisted Supramolecular Self-assembly of 2-acetylamino-6-methylpyridine-N-oxide and Hetero-assembly of 1:1 Co-crystal of o-Phenylenediamine with Catechol

Abstract Water assisted supramolecular structures of 2-acetylamino-6-methylpyridine-1-oxide (1) and 1:1 complex of o-phenylenediamine with catechol (2) were determined. The crystal structure of 2-acetylamino-6-methylpyridine-1-oxide. H2O (1), triclinic, a = 7.1276 (6), b = 7.8860 (6), c = 8.9938 (7) Å, α = 100. 143 (2), β = 91.493 (2), γ = 110.972 (1)°, V =462.47 (6) Å3, Z = 2, D calc = 1.323 mg.m−3(293°K) reveals a novel centrosymmetric supramolecular assembly that is sustained by water molecules linking the dimers of pyridine-1-oxide through C—H…O, N—H…O, N+—O− … H hydrogen bonds. The pyridine rings of the dimers are stacked at 3.473 Å apart, involving π- stacking interactions. Complex (2), C6H8N2.—C6 H6O2. 1/2H2O crystallises in the monoclinic space group P2/c: a = 9.0498(2), b = 5.2275(1), c = 25.0771(2) A, β = 97.71°, V= 1175.62(4) Å3, Z = 4. Refinement led to a final conventional R value of 0.041 for 2016 reflections. In these crystals (2), the water molecules lie on the twofold axis and they are linked to the pyrocatechol molecules through an O—H…O hydrogen bond.

2-Acetylamino-6-methylpyridine N-oxide monohydrate

In the title molecule, C 8 H 10 N 2 O 2 .H 2 O, the acetylamino group forms a dihedral angle of 6.05 (6)° with the pyridine ring. The N-H…O, O-H…O and C-H…O hydrogen bonds, along with π-π stacking interactions, are involved in the formation of a supramolecular assembly, with the water molecule acting as a bridging ligand.