Structural Characterization, DFT Calculation, NCI, Scan-Rate Analysis and Antifungal Activity against Botrytis cinerea of (E)-2-{[(2-Aminopyridin-2-yl)imino]-methyl}-4,6-di-tert-butylphenol (Pyridine Schiff Base)

Abstract

Botrytis cinerea is a ubiquitous necrotrophic filamentous fungal phytopathogen that lacks host specificity and can affect more than 1000 different plant species. In this work, we explored L1 [(E)-2-{[(2-aminopyridin-2-yl)imino]-methyl}-4,6-di-tert-butylphenol], a pyridine Schiff base harboring an intramolecular bond (IHB), regarding their antifungal activity against Botrytis cinerea. Moreover, we present a full characterization of the L1 by NMR and powder diffraction, as well as UV–vis, in the presence of previously untested different organic solvents. Complementary time-dependent density functional theory (TD-DFT) calculations were performed, and the noncovalent interaction (NCI) index was determined. Moreover, we obtained a scan-rate study on cyclic voltammetry of L1. Finally, we tested the antifungal activity of L1 against two strains of Botrytis cinerea (B05.10, a standard laboratory strain; and A1, a wild type strains isolated from Chilean blueberries). We found that L1 acts as an efficient antifungal agent against Botrytis cinerea at 26 °C, even better than the commercial antifungal agent fenhexamid. Although the antifungal activity was also observed at 4 °C, the effect was less pronounced. These results show the high versatility of this kind of pyridine Schiff bases in biological applications.

Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria

“…For SB-1, the FTIR spectrum showed bands that are generally considered symmetric and asymmetric stretching νOH vibrations at 3475.73 cm −1 assigned to the IHB ( Figure S14 ). This assignment is consistent with previously reported signals assigned to similar Schiff bases [ 26 ]. Two additional bands were observed at 3379.29 and 3059.10 cm −1 , assigned to the νNH stretching vibrations modes (asymmetric and symmetric) of a primary amino group, in accordance with previously reported results for comparable Schiff bases [ 26 ].…”

“…This assignment is consistent with previously reported signals assigned to similar Schiff bases [ 26 ]. Two additional bands were observed at 3379.29 and 3059.10 cm −1 , assigned to the νNH stretching vibrations modes (asymmetric and symmetric) of a primary amino group, in accordance with previously reported results for comparable Schiff bases [ 26 ]. We assigned the bands at 2962.66 cm −1 , 2866.22 cm −1 , and 2530.61 cm −1 as typical νC–H bands.…”

“…To distinguish compound-related REDOX processes from secondary reactions with the solvent (e.g., acetonitrile), a working window study is mandatory ( Figures S17 and S18 ) [ 22 ]. Similar profiles have been described for similar Schiff bases with an IHB [ 22 , 26 ].…”

“…Other absorptions were observed at 1666.50 cm −1 , 1616.35 cm −1 , and 1570.06 cm −1 , assigned as νC=O (carbonyl group), νHC=N (azomethine), and νC=C, respectively. Although the azomethine group is usually assigned to absorptions at around 1640 cm −1 [ 27 ], the SB-1 azomethine group (1616.35 cm −1 ) can be explained by the presence of the IHB, as described for other similar molecules [ 26 ]. SB-2, for its part, showed a characteristic pattern in line with previous studies [ 25 ] ( Figure S15 ).…”

The role of substituted pyridine Schiff bases as ancillary ligands in the optical properties of a new series of fac-rhenium(i) tricarbonyl complexes: a theoretical view

“…We previously characterized these PSBs regarding their structural, optical, electronical and antimicrobial properties. [39][40][41][42] On the other hand, the PSBs (E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6di-methylphenol (PSB1), and (E)-2-(((4-aminopyridin-3-yl)imino) methyl)-4-methylphenol (PSB2), to our knowledge, are new (Scheme 1). In the present study, we worked with two series of Re(I) tricarbonyl complexes with their respective PSB ligands (PSB1 to PSB6, Scheme 1), which are summarized in Table S1: † (1) fac-[Re(CO) 3 (2,2 0 -bpy)(PSB)] 1+ (Fig.…”