Abstract
The calix[4]arene molecule, abbreviated as CX[4], is known by the four phenolic groups and a hydrophobic cavity able to enclose small molecules. The interactions between CX[4] and NO3, NO2, CO2, and N2 gas molecules have been studied. These guest species are placed inside and outside the cavity of the host molecule CX[4]. The formation of H-bonding has been deeply discussed based on the infrared spectrum and the polarizability analysis. Global and local indices have been calculated for a series of gas (NO3, NO2, CO2 and N2) in interaction with the CX[4] molecule to explain the electrophilic or nucleophilic activations in endo-vs. exo-cavity interaction zone. As expected, there is a correlation between the proposed global electrophilicity and global nucleophilicity together for an explanation of the chemo-selectivity region. Finally, the topological parameter analyses of the host-guests interactions have been estimated by using DFT calculations.
Highlights
The selectivity of the anionic or cationic guests in microscopic or macroscopic systems facilitates the recognition of the magnetic and electrostatic properties of the several guests’ complexes [1, 2, 3, 4, 5]
By using Density Functional Theory (DFT) calculations, we have described the dynamic stabilities of the endo-vs. exo-cavity of the CX[4]-gas complexes
The optimization of CX[4] and CX[4]-gas have been performed by the Density Functional Theory (DFT) method by using the global hybrid generalized gradient approximation B3LYP [15, 18, 19, 20] coupled to the D3BJ in combination with the 6-31þG(d) basis set, as implemented in a Gaussian 09 package [21] and the GaussView [22] as a visual program
Summary
The selectivity of the anionic or cationic guests in microscopic or macroscopic systems facilitates the recognition of the magnetic and electrostatic properties of the several guests’ complexes [1, 2, 3, 4, 5]. The CX[4] is characterized by a specific height and a diameter, these two parameters facilitate the complexation with small molecules [7, 8, 9]. We have studied the physical and chemical properties of the CX[4]-NO3, CX[4]-NO2, CX [4]-N2 and CX[4]-CO2 complexes (The specific gas in the endo or exo-cavity position). We have discussed the interactions between the CX [4] molecule and NO3, NO2, CO2 and N2 gases outside or inside the cavity. The encapsulation of these gases may be a good subject for pollution. The recognition of the weak or the strong and the nature of the interactions of such guest with a cage molecule have been analyzed by the AIM topological parameters
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