Synthesis, Molecular Structure, and Properties of a Neutral Schiff Base Phenolic Complex of Magnesium

Abstract

A neutral bis(salicylaldimine) Mg complex has been synthesized, representing the first stable Schiff base phenoxo complex of Mg involving the participation of two phenolic oxygens and four nitrogens. While the crystal structure of the Mg complex was determined to be highly similar to those of known cationic Ga(III) and Fe(III) complexes, in contrast, the Mg complex did not show significant differential cytotoxicity between drug-sensitive and multidrug-resistant cancer cells expressing MDR1 P-glycoprotein.

Metal Complexes for Therapy and Diagnosis of Drug Resistance

“…1 H NMR data suggested that 85% of the parent compound remained after a 72 h incubation in solution containing an equimolar mixture of Mg 2+ and HPO 4 2- /H 2 PO 4 - ions at pH 7.4. Lowering the pH or deleting Mg 2+ ions increased the rate of hydrolysis . Cytotoxicity studies (Figure ) in non-Pgp- and Pgp-expressing tumor cell lines demonstrated that the cytotoxicity profiles were not modified by expression of MDR1 Pgp.…”

“…Lowering the pH or deleting Mg 2+ ions increased the rate of hydrolysis. 94 Cytotoxicity studies (Figure 2) in non-Pgp-and Pgp-expressing tumor cell lines demonstrated that the cytotoxicity profiles were not modified by expression of MDR1 Pgp. These data suggested that compound 25 was not interacting with Pgp.…”

“…A neutral Mg complex of N,N′-bis{3-[(2-hydroxy-3-methoxybenzyl)imino]pro-pyl}ethylenediamine (25), incorporating a Schiff-base phenolic ligand structurally similar to the analogous Ga(III) complex, was synthesized by a one-step condensation reaction. 94 1 H NMR data suggested that 85% of the parent compound remained after a 72 h incubation in solution containing an equimolar mixture of Mg 2+ and HPO 4 2-/H 2 PO 4ions at pH 7.4. Lowering the pH or deleting Mg 2+ ions increased the rate of hydrolysis.…”

“…To further explore the impact of the charge of a candidate agent in promoting interactions with Pgp, a neutral analogue of these Ga(III) complexes was synthesized. A neutral Mg complex of N , N ‘ -bis{3-[(2-hydroxy-3-methoxybenzyl)imino]propyl}ethylenediamine ( 25 ), incorporating a Schiff-base phenolic ligand structurally similar to the analogous Ga(III) complex, was synthesized by a one-step condensation reaction …”

Mg2+-Induced Thermal Enediyne Cyclization at Ambient Temperature

“…Although modest (<0.5 ppm) chemical shift changes are observed due to the presence of radical-mediated decomposition product, 17 To evaluate the structural consequences giving rise to such facile thermal reactivity, molecular mechanics calculations at the MMX force field level 18 have been performed for enediyne ligand 3, as well as a series of four-to six-coordinate Mg 2+ structures. Since Mg 2+ is electrophilic and frequently forms five-coordinate [19][20][21][22][23] or six-coordinate 21,[24][25][26][27][28][29][30][31] structures in the presence of anionic ligands and coordinating solvents, the geometric starting point for the latter calculations was the five-or six-coordinate MgN 4 O x (x ) 1, 2) construct where OHwas used to approximate solvent (MeOH) or counterion (Cl -) coordination in solution. Within these coordination environments, approximately 60 structures were iteratively minimized until a subset of five of the lowest-energy structures for each class were identified.…”