Cd^II-Mediated Efficient Synthesis and Complexation of Asymmetric Tetra-(2-pyridine)-Substituted Imidazolidine

Abstract

One convenient Cd II -mediated C−C/C−N bond-forming strategy toward asymmetric tetra-(2-pyridine)substituted imidazolidine (L 1 ), the basic framework of several natural products with bioactivity, has been found for the first time. In the reaction of tridentate N3-set neutral pyridine-type Schiff base ligand (L) possessing a [−HCNCH 2 −] linkage with CdCl 2 at 70 °C for 3 days, one two-dimensional 4 4 topological layer [Cd 3 L 1 Cl 6 ] n (1) could be obtained, in which ligand L 1 resulted from [3 + 2] C−C/C−N asymmetric coupling dimerization of L. When equimolar amounts of NaSCN and NaNO 3 were added to the reaction mixtures, one-dimensional chain [Cd 2 L 1 (SCN)Cl 3 ] n (2) and zero-dimensional dinuclear Cd 2 L 1 (NO 3 ) 4 (MeOH) ( 3) containing the same ligand L 1 were also generated under the same reaction conditions, respectively. Obviously, the medium of the Cd 2+ ion plays the key role in solvothermal in situ formation of ligand L 1 . Moreover, new ligand tetra-substituted imidazolidine (L 1 ) could be obtained effectually from all three complexes 1−3 through the reactions of those compounds with Na 2 S.

Tetranuclear and 1D Polymeric Cd(II) Complexes with a Tetrapyridyl Imidazolidine Ligand: Synthesis, Structure, and Fluorescence Sensing Activity

“…Structurally characterized Cd complexes of different dimensionalities with the ligand L 1 have already been reported. 54,55 In all cases the aza-heterocycle L 1 ligand has a strong propensity to connect Cd metals as described here to form Cd−L 1 −Cd units with intermetallic distances between 6.22 and 6.31 Å.…”

“…N -(2-Pyridylmethyl)­pyridine-2-carbaldimine (L) was prepared by refluxing pyridine-2-aldehyde and 2-picolylamine in methanol according to the literature method, and the ligand 2,2′,2″-(1-(pyridin-2-ylmethyl)­imidazolidine-2,4,5-triyltripyridine) (L 1 ) , was generated in situ by a cadmium-catalyzed reaction from the pyridine-type Schiff base L. 1 H NMR for L (400 MHz, CDCl 3 , δ ppm): 2.918 (2H, s), 7.045–7.186 (1H, m), 7.201–7.264 (1H, d), 7.286–7.381 (1H, m), 7.533–7.594 (1H, m), 7.594–7.688 (1H, m), 7.963–8.443 (1H, d), 8.220 (1H, s), 8.421–8.513 (1H, d), 8.513–8.625 (1H, d).…”

“…Synthesis of Ligand L. N-(2-Pyridylmethyl)pyridine-2-carbaldimine (L) was prepared by refluxing pyridine-2-aldehyde and 2picolylamine in methanol according to the literature method, 54 and the ligand 2,2′,2″-(1-(pyridin-2-ylmethyl)imidazolidine-2,4,5-triyltripyridine) (L 1 ) 54,55 was generated in situ by a cadmium-catalyzed reaction from the pyridine-type Schiff base L. 1 (2). The complex was synthesized by following the same procedure as adopted for complex 1, except using a…”

Molecular Packing Dependent Solid State Fluorescence Response of Supramolecular Metal–Organic Frameworks: Phenoxo-Bridged Trinuclear Zn(II) Centered Schiff Base Complexes with Halides and Pseudohalides

“…Luminescent compounds are attracting current research interest because of their vast applications in emitting materials for solid state organic light emitting diodes, light harvesting materials for photocatalysis, lasers, fluorescent sensors for organic or inorganic analyses, and as biological materials with explosive mimics. − Zinc Schiff bases complexes have been extensively studied for their interesting photophysical properties. , Spectroscopic experiments suggest that coordination to a Zn­(II) center would influence the molecular aggregation via noncovalent interactions such as electrostatic interactions, stacking, and hydrogen bonding. By modifying these interactions, assembly of new materials with exciting properties may be generated. − For example, the use of “salen” style Schiff base ligands can lead to a variety of supramolecular assemblies that can determine their spectroscopic and photophysical properties in solution in relation to the nature of molecular aggregation. The d 10 configuration of Zn­(II) allows architecting flexible coordination environments, thus forming metal complexes with tetrahedral to octahedral geometries, which is an essential criterion for designing a wide variety of metal–organic frameworks that may have interesting photophysical properties.…”

Halide Ion Mediated Aldehyde‐Amine Condensation Leading to Schiff–base and Cyclized Non‐Schiff–base Ligand Complexes of CdII: A Combined Experimental and Theoretical Investigation

“…Metal ions having d 10 electronic configuration are observed to be more prone to exhibit structural diversity owing to their softness and lack of LFSE. Amongst the post‐transition metals, Cd(II) shows better ability in adopting several coordination numbers and structural motifs and in recent time the importance of Cd(II) in bioinorganic chemistry with the discovery of Cd(II) containing carbonic anhydrase as well as in making emitting materials has boosted research on the coordination chemistry of Cd(II) . The nature of co‐ligands is another parameter in controlling structural diversity .…”