Influences of Chemical Functionalities on Crystal Structures and Electrochemical Properties of Dihydro-benzoxazine Dimer Derivatives

Abstract

Dihydro-1,3,2H-benzoxazine dimer derivatives or dihydro-benzoxazine dimers are a class of compounds typically prepared by ring-opening reactions between dihydro-benzoxazines and phenols. Dihydro-benzoxazine dimers act as chelating agents for several transition and rare-earth cations. To better understand the chelating properties, it is necessary to examine their structural features and electrochemical characteristics thoroughly. However, the electrochemical properties of dihydro-benzoxazine dimers have not been tremendously examined. Herein, eight derivatives of dihydro-benzoxazine dimers possessing different substituents on the benzene ring and the tertiary-amine nitrogen were synthesized as model compounds to investigate their influences on crystal structures and electrochemical properties. The crystal structure of the dihydro-benzoxazine dimer, namely 2,2’-(cyclohexylazanediyl)bis(methylene)bis(4-methoxyphenol) (7), is identified for the first time and further used to compare with the crystal structures of other derivatives reported previously. For all the derivatives, intermolecular O–H···O hydrogen bonds are the significant interactions to hold the crystal packing of (7) and also the other derivatives. Hirshfeld surface analyses confirm the presence of intermolecular O–H···O hydrogen bonds. Redox behavior of the eight dihydro-benzoxazine dimers was studied by cyclic voltammetry. An oxidation peak observed at 0.25–0.47 V corresponds to the oxidation of the phenolic –OH group to the phenoxonium intermediate. The shift in the electrochemical peak positions is due to the different abilities of the substituents to stabilize the phenoxonium cation intermediate. The stabilizing power is ranged in the following order: methoxy > dimethyl > ethyl ≈ methyl, and N-cyclohexyl > N-methyl. Thus, the derivative (7), which contains both the methoxy and N-cyclohexyl groups, has the lowest oxidation potential. Our work elucidates the effect of the substituents on the crystal structures and electrochemical properties of the dihydro-benzoxazine dimers.

Partially Bio-Based Benzoxazine Monomers Derived from Thymol: Photoluminescent Properties, Polymerization Characteristics, Hydrophobic Coating Investigations, and Anticorrosion Studies

“…Moreover, the broad peak centered at 3380 cm −1 can be assigned to the presence of the OH functional group formed by ring-opening polymerization. The OH peak of the cured products of the benzoxazines is found at a significantly higher wavenumber than the OH of thymol as the OH groups of the polybenzoxazines are capable of forming intramolecular O-H•••N and intermolecular O-H•••O hydrogen bonds [7,50,52,53]. It is further recognized that the intensity of the OH band increases as the curing temperature increases, as seen in Figures S9-S12 and Tables S1-S4.…”

6,6′-((Methylazanedyl)bis(methylene))bis(2,4-dimethylphenol) Induces Autophagic Associated Cell Death through mTOR-Mediated Autophagy in Lung Cancer

“…Substitution with methyl groups at 2 and 4 positions on benzene ring in 24MD and 24CD provided these compounds a critical potential in stabilizing the cationic intermediates; the cation can be distributed to 2 and 4 positions on the benzene ring due to the effect of the hydroxyl group. The steric effect of substituents in 24CD molecules might promote the formation of intramolecular hydrogen bond (HB) [ 21 ], resulting in the subtraction of a couple of donor/acceptor functional motifs. The intramolecular HB could increase lipophilicity and enhance membrane permeability [ 46 ] while reducing aqueous solubility [ 47 ].…”

“…Three N,N -bis(2-hydroxybenzyl) alkylamines, namely 2,2′-(methylazanediyl)bis(methylene)bis(4-ethylphenol) (EMD), 6,6′-(methylazanediyl)bis(methylene)bis(2,4-dimethylphenol) or (24MD), and 6,6′-(cyclohexylazanediyl)bis(methylene)bis(2,4-dimethylphenol) or (24CD), were synthesized according to the reactions illustrated in Figure 5 [ 21 , 50 , 51 , 52 , 53 ]. The first step was a one-pot Mannich reaction to form benzoxazine heterocycles, and the second step was a ring-opening reaction of the benzoxazines and phenols.…”

“…6,6′-((methylazanedyl)bis(methylene))bis(2,4-dimethylphenol) or 24MD is a benzoxazine dimer analog obtained from ring-opening reactions between dihydro-benzoxazines and phenols [ 21 ]. Previous studies have demonstrated the anticancer effect of another benzoxazine dimer analog, 2,2′-((methylazanedyl)bis(methylene))bis(4-ethylphenol) or EMD [ 22 , 23 ].…”

Analysis of Protein–Protein Interactions Identifies NECTIN2 as a Target ofN,N-Bis(5-Ethyl-2-hydroxybenzyl) Methylamine for Inhibition of Lung Cancer Metastasis

“…EMD and MeMD were synthesized as previously described (15)(16)(17)(18). In brief, EMD and MeMD, benzoxazine dimers (Figure 1A), were synthesized in two steps according to Figure 1B.…”