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Review
. 2018 Jun 27;8(41):23294-23318.
doi: 10.1039/c8ra01890a. eCollection 2018 Jun 21.

Acyclic and cyclic imines and their metal complexes: recent progress in biomaterials and corrosion applications

Affiliations
Review

Acyclic and cyclic imines and their metal complexes: recent progress in biomaterials and corrosion applications

Wail Al Zoubi et al. RSC Adv. .

Abstract

This review describes the contemporary development applications on scientific areas of acyclic and cyclic Schiff bases and their complexes with an emphasis on the author's contribution to the field. After a short historical introduction, this manuscript is divided into two main parts. In the first section, Schiff bases are reviewed for their biological activities including antibacterial, antifungal, antioxidant, cytotoxic, and enzymatic activities as well as their interaction with single-stranded-DNA which have shown remarkable activities in each region of research. The second part deals with the corrosion of metal and its alloys in corrosive environments and their organic inhibitors. The main section of this part is to investigate the different chemical structures for Schiff bases used in such aggressive solution to protect metals. Knowing the maximum corrosion efficiency or bioactivity of a specific chemical structure in a specific application environment is helpful for choosing the most appropriate compound.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Synthesis of Cu(ii) complexes [Cu(L1)2–Cu(L4)2].
Scheme 2
Scheme 2. Synthesis of complexes M(L1)PPh3–M(L4)PPh3.
Scheme 3
Scheme 3. Synthesis of Schiff base complexes (a–c).
Scheme 4
Scheme 4. Synthesis of imines (HL1–HL4).
Scheme 5
Scheme 5. Structures of the ligands and the formation of complexes 1–3.
Scheme 6
Scheme 6. Structures of SBs (L1 and L2).
Scheme 7
Scheme 7. Synthesis of the copper complexes from bis(dithiocarbazate) ligands. Reagents and conditions: (a) CS2, KOH, EtOH, 0 °C, 1 h; (b) CH3I or PhCH2Cl, EtOH, 0 °C, 5 h; (c) for SMHDH2 (2,5-hexanedione, EtOH, 79 °C, 1 h), for SBHDH2 (2,5-hexaedione, EtOH, 79 °C, 5 min) and (d) for CuSMHD [Cu(OAC)2·H2O, MeOH, 65 °C, 1 h], for CuSBHD [Cu(OAc)2, acetonitrile, r.t, 1 h].
Fig. 1
Fig. 1. Structures of Schiff bases 1a–1k and their corresponding secondary amines 3a–3k showing the numbering system used in the assignment of 1H and 13C NMR spectra.
Scheme 8
Scheme 8. Synthesis of SB ligands.
Scheme 9
Scheme 9. Preparation of Schiff bases (SBs).
Scheme 10
Scheme 10. (I) Synthesis route to Schiff bases of 5-substituted isatins. (II) Synthetic routes to compound 7 and Schiff bases of N-arylmethylisatin 11a–13c. Reagents and conditions: (a) phenylhydrazine, ethanol 96% (w/w), acetic acid; (b) fluorinated benzyl chlorides, K2CO3, KI, acetonitrile; (c) compounds 8–10, ethanol 96% (w/w), acetic acid.
Scheme 11
Scheme 11. Synthesis of bis-Schiff from isatins.
Scheme 12
Scheme 12. Synthetic route for SBs.
Scheme 13
Scheme 13. Synthetic pathway for the protection of target compounds 2, 3, 4, 5, 6 and 7.
Scheme 14
Scheme 14. Synthesis of copper complexes [Cu(L1)2–Cu(L3)2].
Scheme 15
Scheme 15. Synthesis of Schiff bases 1–5.
Scheme 16
Scheme 16. Synthesis of C6-Schiff bases of chitosan derivatives.
Scheme 17
Scheme 17. Synthesis of chitosan Schiff bases (ChBs).
Scheme 18
Scheme 18. Modification of chitosan-graft-polyacrylonitrile.
Scheme 19
Scheme 19. Schematic representation of ionic liquid-anchored chitosan Schiff bases and their metal complexes.
Scheme 20
Scheme 20. Synthetic route for the preparation of SBs.
Fig. 2
Fig. 2. Molecular structure of investigated SBs (P1: X = H; P2: X = Cl; P3: X = Br).
Fig. 3
Fig. 3. Optimized geometrical configurations of BFBT, TMBT, and FNBT.
Fig. 4
Fig. 4. (((5-Phenyl-1,3,4-thiadiazol-2-yl)imino)quinolone-2-ol/thiol).
Fig. 5
Fig. 5. Structures of studied Schiff bases.
Fig. 6
Fig. 6. Chemical structure of the investigated compounds.
Fig. 7
Fig. 7. Chemical structure of the tested SBs.
Fig. 8
Fig. 8. Structure of inhibitor molecule.
Scheme 21
Scheme 21. Representation procedures for the synthesis of Schiff base compounds.
Scheme 22
Scheme 22. Synthetic route for investigated SBs.
Scheme 23
Scheme 23. Chemical structure of Schiff base molecules S1 and S2.
Scheme 24
Scheme 24. Synthesis of ferrocene carboxaldehyde propanoylhydrazone (fcph) and ferrocene carboxaldehyde furoylhydrazone (fcfh) Schiff bases.
Scheme 25
Scheme 25. Reaction pathway showing the formation (E)-4-((naphthalen-2-ylimino)methyl)phenol Schiff base.
Scheme 26
Scheme 26. Reaction route for the preparation of (a) (Z)-N-(2-chlorobenzyllidene)naphthalene-1-amine, and (b) (Z)-N-(3-nitrobenzyllidene)naphthalene-1-amine.
Scheme 27
Scheme 27. Reaction of vanillin with isoniazid.
Fig. 9
Fig. 9. Chemical structures of the Schiff bases.
Fig. 10
Fig. 10. Chemical structures of the synthesized inhibitors.
Fig. 11
Fig. 11. Chemical structure of the synthesized corrosion inhibitors: (a) N′-(4-hydroxybezylidene)nicotinic hydrazone (HBNH), and (b) N′-(4-methylbezylidene)nicotinic hydrazone (MBNH).
Fig. 12
Fig. 12. Chemical structures of the synthesized SBs.
Fig. 13
Fig. 13. Structure of the investigated SBs.
Fig. 14
Fig. 14. Chemical structure of SBs.
Fig. 15
Fig. 15. Names and structures of the investigated SBs.
Fig. 16
Fig. 16. Synthesis route of the studied compounds: (a) 4-(dimethylamino)benzaldehyde, (b) aniline, (c) (E)-N,N-dimethyl-4-((phenylimino)methyl)aniline (E-NDPIMA), (d) diethylphosphite, and (e) diethyl ((4-(dimethylamino)phenyl)(phenylamino)methyl)phosphonate (α-APD).
Fig. 17
Fig. 17. General structure of the investigated SBs.
Fig. 18
Fig. 18. Schiff bases.
Fig. 19
Fig. 19. Structure of the investigated SBs: 3-(5-nitro-2-hydroxybenzylideneamino)-2-(5-nitro-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (NNDQ).
Fig. 20
Fig. 20. Structure of the studied SBs.

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