Structural Diversity of Hydrogen-Bonded 4-Aryl-3,5-Dimethylpyrazoles for Supramolecular Materials.

Sandra Moyano,Leire San Felices,Anabel Elduque,Raquel Giménez,Beatriz Diosdado

doi:10.3390/ma14164550

Abstract

The 1H-pyrazoles have high versatility and ability to form hydrogen-bonded supramolecular materials. In this study, the thermal stability, fluorescence, and H-bonding ability of the studied 3,5-dimethyl-4-(4-X-phenyl)-1H-pyrazoles showed large differences depending on the terminal substituent. Supramolecular structures were analyzed using X-ray diffraction and Hirshfeld surface calculations. Compounds were found to arrange in different hydrogen-bonded structures, depending on the substitution at the para position of the phenyl ring (X = OCH3, NO2, NH2). The methoxy-substituted compounds arranged in dimers through methanol bridges, the nitro-substituted compound formed supramolecular polymers or catemers, and the amino-substituted compound gave rise to a new structure based on a 2D hydrogen-bonded network.

Highlights

Hydrogen-bonded supramolecular materials are being investigated in diverse research areas such as for drug development [1], energetic materials [2], porous supramolecular organic frameworks [3], or functional soft materials [4,5]
The precursory 1,3-diketones were synthesized through a copper-catalyzed arylation reaction of acetylacetone with p-iodomethoxybenzene or p-iodonitrobenzene [12]; details are given in Materials and Methods
The thermal properties of the as-obtained pyrazoles were analyzed by optical microscopy, thermogravimetry (TGA), and differential scanning calorimetry (DSC)

Summary

Introduction

Hydrogen-bonded supramolecular materials are being investigated in diverse research areas such as for drug development [1], energetic materials [2], porous supramolecular organic frameworks [3], or functional soft materials [4,5]. The pyridine-type nitrogen (N2), allow hydrogen-bonded interactions to be established with different topologies (monodentate, exobidentate) [8,9], as well as multiple bridge modes to be established between pyrazole cycles such as dimers, trimers, tetramers, or polymeric structures (catemers) [10,11]. Such structural diversity and the dynamic character of the hydrogen bonds mean pyrazole derivatives have great potential for the development of functional materials.

Methods

Results

Conclusion