Special Issue "Schiff-Base Metal Complexes"

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Coordination Chemistry".

Deadline for manuscript submissions: closed (30 November 2017).

Special Issue Editor

Prof. Dr. Santo Di Bella
E-Mail Website
Guest Editor
Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale A. Doria 6, I-95125 Catania, Italy
Interests: functional molecular materials; molecular aggregation; sensing; transition metal complexes; zinc; nonlinear optical properties

Special Issue Information

Dear Colleagues,

Schiff-base metal complexes represent one of most popular and studied families of coordination compounds. Thanks to their relatively simple and flexible synthetic routes, which allow the achievement of many structures, and the variability of the electronic and structural properties induced by the coordinated metal center, these compounds exhibit many characteristics. Moreover, the combination of these features gives the possibility to design and synthesize new molecular architectures with versatile, desired properties. Therefore, these classical coordination compounds have recently emerged as molecular multifunctional materials. Indeed Schiff-base metal complexes are involved as crystalline, polymeric, supramolecular, mesogenic, nanostructured materials or metal-organic frameworks, having variegated photophysical, magnetic, and electronic properties, with potential application as functional materials in the field of catalysis, as sensors, OLED, solar cells, and cell imaging. Much of the interest for this family of complexes is also related to their antimicrobial/antibacterial activity. Hence, Schiff-base metal complexes are classical compounds for modern applications under continuous development.

This Special Issue aims to provide a collection of reviews and research articles on recent advances in all the above aspects involving metal Schiff-base complexes, to offer to researchers and readers a forum of discussion and scientific exchange.

Prof. Dr. Santo Di Bella
Guest Editor

Manuscript Submission Information

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Keywords

  • Schiff-base complexes
  • Synthetic methods
  • Supramolecular chemistry
  • Metal-organic frameworks
  • Nanostructured materials
  • Molecular sensors
  • Catalysis
  • Optical and magnetic properties
  • Mesogenic properties
  • Antimicrobial/antibacterial activity

Published Papers (6 papers)

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Research

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Open AccessArticle
Reaction of Non-Symmetric Schiff Base Metallo-Ligand Complexes Possessing an Oxime Function with Ln Ions
Inorganics 2018, 6(1), 33; https://doi.org/10.3390/inorganics6010033 - 09 Mar 2018
Abstract
The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral [...] Read more.
The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral non-symmetric CuII or NiII metallo-ligand complexes under their mono- or di-deprotonated forms. In presence of Lanthanide ions the neutral complexes do not coordinate to the LnIII ions, the oxygen atom of the oxime function being only hydrogen-bonded to a water molecule that is linked to the LnIII ion. This surprising behavior allows for the isolation of LnIII ions by non-interacting metal complexes. Reaction of cationic NiII complexes possessing a protonated oxime function with LnIII ions leads to the formation of original and dianionic (Gd(NO3)5)2− entities that are well separated from each other. This work highlights the preparation of well isolated mononuclear LnIII entities into a matrix of diamagnetic metal complexes. These new complexes complete our previous work dealing with the complexing ability of the oxime function toward Lanthanide ions. It could open the way to the synthesis of new entities with interesting properties, such as single-ion magnets for example. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessCommunication
A Cryptand-Type Aluminum Tris(salophen) Complex: Synthesis, Characterization, and Cell Imaging Application
Inorganics 2018, 6(1), 20; https://doi.org/10.3390/inorganics6010020 - 24 Jan 2018
Cited by 2
Abstract
Metal salen/salophen complexes have been used as fluorescent probes for cell imaging with various metal centers. Herein we synthesized cryptand-type aluminum salophen complexes LAl3 and the corresponding mononuclear compound LAl. X-ray crystal diffraction verifies the cryptand-type structure of LAl3 with C [...] Read more.
Metal salen/salophen complexes have been used as fluorescent probes for cell imaging with various metal centers. Herein we synthesized cryptand-type aluminum salophen complexes LAl3 and the corresponding mononuclear compound LAl. X-ray crystal diffraction verifies the cryptand-type structure of LAl3 with C3h symmetry. Both LAl3 and LAl show moderate green fluorescence with quantum yields of 0.17 and 0.05, respectively. The hydrophilic and cationic nature of these aluminum salophen complexes renders them enhanced cellular uptake. Both complexes are internalized into cells by energy-dependent pathways and they distribute in lysosomal organelles. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessArticle
Supramolecular Aggregation of a New Substituted Bis(salicylaldiminato)zinc(II) Schiff-Base Complex Derived from trans-1,2-Diaminocyclohexane
Inorganics 2018, 6(1), 8; https://doi.org/10.3390/inorganics6010008 - 01 Jan 2018
Cited by 4
Abstract
In this contribution is reported the synthesis, characterization, and aggregation properties in solution of a novel Zn(II) complex, (R)-2, derived from the enantiopure chiral trans-1,2-diaminocyclohexane and a substituted salicylaldehyde. Detailed 1H NMR, DOSY NMR, optical absorption, and [...] Read more.
In this contribution is reported the synthesis, characterization, and aggregation properties in solution of a novel Zn(II) complex, (R)-2, derived from the enantiopure chiral trans-1,2-diaminocyclohexane and a substituted salicylaldehyde. Detailed 1H NMR, DOSY NMR, optical absorption, and circular dichroism spectroscopic studies and chemical evidence allowed to investigate the nature of aggregate species in solution. The high solubility of (R)-2 in solution of the non-coordinating chloroform solvent leads to formation of various aggregates, some of them consisting of large oligomers estimated to contain up to 27 monomeric units. The chiral trans-stereochemistry of the bridging diamine favors a different aggregation mode in these complexes, both in the oligomers and dimers, involving a tetrahedral coordination geometry around the metal center. Overall data suggest the formation of helical oligomers, (ZnL)n, in freshly prepared chloroform solutions which, by standing or heating, evolve towards a more thermodynamically stable, dinuclear double-helicate Zn2L2 dimer. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessArticle
Pentacoordinated Chloro-Iron(III) Complexes with Unsymmetrically Substituted N2O2 Quadridentate Schiff-Base Ligands: Syntheses, Structures, Magnetic and Redox Properties
Inorganics 2018, 6(1), 5; https://doi.org/10.3390/inorganics6010005 - 29 Dec 2017
Cited by 2
Abstract
Since their development in the 1930s, Schiff-base complexes have played an important role in the field of coordination chemistry. Here, we report the synthetic, spectral, structural, magnetic and electrochemical studies of two new pentacoordinated neutral chloro-iron(III) complexes (3,5) supported [...] Read more.
Since their development in the 1930s, Schiff-base complexes have played an important role in the field of coordination chemistry. Here, we report the synthetic, spectral, structural, magnetic and electrochemical studies of two new pentacoordinated neutral chloro-iron(III) complexes (3,5) supported by dianionic [N2O2]2− tetradentate Schiff-base ligands unsymmetrically substituted by either a pair of acceptor (F and NO2) or donor (ferrocenyl and OCH3) groups. The electron-withdrawing Schiff-base proligand 2 and the complexes 3 and 5 were prepared in good yields (79–86%). Complex 3 was readily obtained upon reaction of 2 with anhydrous iron chloride under basic conditions, while the bimetallic derivative 5 was synthesized by condensation of the free amino group of the ferrocenyl-containing O,N,N-tridentate half-unit 4 with 5-methoxysalicylaldehyde in the presence of FeCl3. The three new compounds were characterized by elemental analysis, FT-IR, UV–Vis, mass spectrometry and in the case of 2 by multinuclear NMR spectroscopy. The crystal structures of 3 and 5 revealed that in the two five-coordinate monomers, the iron atom showed distorted square-pyramidal geometry, with the N and O atoms of the Schiff-base ligand occupying the basal sites and the chlorine atom at the apex of the pyramid. Magnetic measurements showed a high-spin configuration (S = 5/2) for the Fe(III) ion in 3 and 5. Reduction associated with the Fe(III)/Fe(II) redox couple occurred at −0.464 and −0.764 V vs. Ag/Ag+, and oxidation taking place at the Schiff-base ligand was observed at 1.300 and 0.942 V vs. Ag/Ag+ for 3 and 5, respectively. A high-electronic delocalization of the Schiff-base ligand substituted by fluoro and nitro groups stabilizes the Fe(II) oxidation state and shifts the redox potential anodically. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessArticle
Assembly of Mn(III) Schiff Base Complexes with Heptacyanorhenate (IV)
Inorganics 2017, 5(3), 59; https://doi.org/10.3390/inorganics5030059 - 01 Sep 2017
Cited by 2
Abstract
A pioneering research on a self-assembly of the magneto-anisotropic module [Re(CN)7]3− with the Mn(III) complexes involving Salen type (N,N′-ethylenebis(salicylideneiminate)) Schiff base (SB) ligands was performed using the known [Mn(3MeOSalen)(H2O)2]2 [...] Read more.
A pioneering research on a self-assembly of the magneto-anisotropic module [Re(CN)7]3− with the Mn(III) complexes involving Salen type (N,N′-ethylenebis(salicylideneiminate)) Schiff base (SB) ligands was performed using the known [Mn(3MeOSalen)(H2O)2]2(ClO4)2·H2O (1) and the firstly synthesized [Mn2(5MeSalen)2OAc]PF6 (2). In the case of 1, a slow diffusion of the component solutions led to the ionic compound Ph4P[Mn(3MeOSalen)(H2O)2]2[Re(CN)7]·6H2O (3). The direct mixing of the same solutions has resulted in the microcrystalline nearly insoluble solid [Mn(3MeOSalen)(H2O))4Re(CN)7]ClO4·1.5MeCN·6.5H2O, which is likely to comprise the pentanuclear clusters [(MnIII(SB)(H2O))4Re(CN)7]+. The use of 2 resulted in a 2D-network assembly of octanuclear clusters, [{(Mn(5MeSalen))6(H2O)2Re(CN)7}2Re(CN)7]Cl2(PF6)·H2O (4), incorporating one Re-center in a pentagonal bipyramid coordination environment, while another has strongly distorted capped trigonal prism as a coordination polyhedron. The latter was observed for the first time for Re(IV) complexes. A synthetic challenge to obtain the 0D assemblies with Re:Mn ≥ 3 has yielded a hexanuclear complex [Mn(5MeSalen)H2O(i-PrOH)][(Mn(5MeSalen))5H2O(i-PrOH)2Re(CN)7](PF6)2(OAc)·2i-PrOH (5) being 1D chain via a bridging phenoxyl group. Owing to a low solubility of the final product, an addition of a bulk anion Ph4B to the MeCN/MeOH solution of [Re(CN)7]3−and 1 in ratio 1:6 resulted in rhenium-free matter [Mn(3MeOSalen)(H2O)2][Mn(3MeOSalen)(H2O)MeCN](Ph4B)2·5MeCN (6). Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Review

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Open AccessReview
The Supramolecular Attitude of Metal–Salophen and Metal–Salen Complexes
Inorganics 2018, 6(2), 42; https://doi.org/10.3390/inorganics6020042 - 24 Apr 2018
Cited by 6
Abstract
In this review we cover some aspects of metal–salophen and metal–salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this [...] Read more.
In this review we cover some aspects of metal–salophen and metal–salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this last point has been only briefly mentioned. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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