Salicyclaldimines (5-9) and naphthaldimines (10-13) derived from condensation reactions of N2O2 donor type bifunctional aminopodands (1-4), [(H2NPhO)2R, where R = CH2CH2, CH2CH2CH2 and CH2PhCH2], and hydrazine monohydrate with salicylaldehyde and 2-hydroxy-1-naphthaldehyde, respectively, have been prepared (scheme 1) and characterized by elemental analyses, UV-vis, FTIR, NMR and MS. NMR assignments were made using 1H, 13C NMR, DEPT and aided by 2D HETCOR and HMBC heteronuclear correlation techniques. The UV-vis spectra of the Schiff bases have been systematically studied in organic solvents of different polarity, acidic and basic media and found useful in understanding of tautomeric equilibria (phenol-imine, O-H…N and keto-amine, O…H-N forms) in this series. The molecular structure of 8 has been determined crystallographically, and observed that the compound is in the form of phenol-imine, defined by the strong intramolecular [O-H…N = $1 \cdots 72$(3), $1 \cdots 81$(2) Å] hydrogen bonds. Compound 8 crystallizes in the monoclinic space group $P2_1/a$ with $a = 8 \cdots 4675$(7), $b = 38 \cdots 448$(3), $c = 9 \cdots 3875$(7) Å, $\beta = 103 \cdots 0780$(10)°, $V = 2976 \cdots 9$(4) Å3, $Z = 4$ and $D_x = 1 \cdots 271$ Mg m-3, and contains acetonitrile molecule in the crystal lattice.
Volume 134, 2022
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