Open access

Introductory Chapter: Chirality from Molecular Electronic States

Written By

Takashiro Akitsu

Published: January 11th, 2019

DOI: 10.5772/intechopen.83835

Chapter metrics overview

914 Chapter Downloads

View Full Metrics

1. Chiral assembly of proteins and metal complexes

Needless to say, chirality is an important concept along the fields of biology, chemistry, and physics. Not only steric fitness (stereochemical aspects) but also electronic properties (or electronic states as origin) may be important in such cases, which is a motivation to emphasis the concept of this book.

In recent years, in order to prepare “artificial metalloproteins” composed of natural proteins (typically egg white lysozyme) including synthesized metal complexes (salen-type Cu(II) complexes), we searched and investigated candidate metal complexes using crystal structure databases (CSD [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24] and PDB). In this context, we used a GOLD program to search well docking features between proteins and ligand of small molecules structurally and obtained docking scores (Table 1). As for molecular structures, DFT calculations from a Gaussian 09 program may be useful to obtain not only optimized structures but also detailed electronic states of metal complexes in principle.

Table 1.

GOLD scores of docking copper(II) complexes into lysozyme. Detailed study of the best four complexes will be reported elsewhere.

At least proteins must be a hard target to discuss. Once I asked to my collaborator of computational chemical physics, “I will ask you DFT calculations of simulated IR spectra of them. Moreover, I also want to know simulated IR spectra of amide I, II, and some other bands for typical proteins such as lysozyme.” Then he replied, “When you’ll send me the data, I’ll continue with the assignment. I don’t know how long do you like the discussion of the vibrational bands, and what are the most interested bands for you. Additionally, strong bands corresponding to intermolecular H-bands appear in the exp. spectrum. If you have the X-ray data of these molecules, I can simulate it and improve the assignments.”

Even employing achiral metal complexes, such hybrid assembly must be a chiral material, which can be experimentally elucidated by means of chiroptical spectroscopy (CD or VCD) [25] as well as quenching of fluorescence intensity (obeying Stern-Volmer plot) [26]. However, calculations of electronic state for such hybrid assembly must be difficult only by means of these conventional or commercially available programs at present [27]. In this way, supramolecular chirality may be one of the challenging targets in near future.

Advertisement

2. Chiral metal complexes by spectroscopy, magnetism, and computational interpretation

In the case of chiral salen-type metal complexes, it is not easy to investigate their electronic properties using both experimental and theoretical methods. Previously, we have systematically studied on preparations, crystal structures, and electronic states for mononuclear (3d) [25, 26, 27] and binuclear (3d-4f) [28, 29, 30, 31, 32] complexes. Besides X-ray crystallography and IR spectra, CD and UV-vis spectra, XAS spectra, fluorescence spectra, and magnetic measurements were used. However, not all methods are valid at the same time for one complex of a certain combination of 3d and 4f metal ions, for example, some complexes were diamagnetic, and some complexes did not exhibit emission. Hence, we also carried out DFT or semiempirical molecular orbital calculations as well as these experiments. However, 4f metal ions having many electrons usually took a long time to calculate with DFT accurately and the results often deviated from the corresponding experimental data largely (for example, simulated CD spectrum shown in Figure 1).

Figure 1.

Simulated UV-vis and CD spectra for La(III)-Cu(II) complex [27].

In conclusion, beyond stereochemical aspects, chirality may be important, though there are limited methods to elucidate their electronic states in particular theoretically such as chiroptical spectra and expanding supramolecular functions at present.

References

  1. 1. Bhadbhade MM, Srinivas D. Effects on molecular association, chelate conformation, and reactivity toward substitution in copper Cu(5-X-salen) complexes, salen2- = N,N’-ethylenebis(salicylidenaminato), X = H, CH3O, and Cl: Synthesis, X-ray structures, and EPR investigations. Inorganic Chemistry. 1993;32:6122-6130. DOI: 10.1021/ic00078a037
  2. 2. Thomas F, Jarjayes O, Duboc C, Philouze C, Saint-Aman E, Pierre JL. Intramolecularly hydrogen-bonded versus copper(II) coordinated mono- and bis-phenoxyl radicals. Dalton Transactions. 2004:2662-2669. DOI: 10.1039/B406009A
  3. 3. Yao HH, Huang WT, Lo JM, Liao FL, Wang SL. European. Journal of Solid State Inorganic Chemistry. 1997;34:355-366
  4. 4. Bunce S, Cross RJ, Farrugia LJ, Kunchandy, S, Meason LL, Muir KW, Odonnell M, Peacock RD, Stirling D, Teat SJ. Chiral Schiff base complexes of copper (II), vanadium (IV) and nickel (II) as oxidation catalysts. X-ray crystal structures of [Cu (R-salpn) (OH2)] and [Cu (±-busalcx)]. Polyhendron. 1998;17:4179-4187
  5. 5. Raisanen MT, Kinga M, Nieger M, Repo T, Structural and spectroscopic characterization of Cu(salen) complexes bearing long alkoxy chains. Journal of Coordination Chemistry. 2010;63:4280-4289. https://doi.org/10.1080/00958972.2010.533762
  6. 6. Paschke R, Balkow D, Sinn E. Lowering Melting Points in Asymmetrically Substituted Salen-Copper(II) Complexes Exhibiting Mesomorphic Behavior. Structure of the Mesogen Cu(5-hexyloxySalen). Inorganic Chemistry. 2002;41:1949-1953. DOI: 10.1021/ic010875u
  7. 7. Freiburg C, Reichert W, Melchers M, Engelen B. N,N’-Ethylenbis(1-iminomethyl-2-naphtholato)kupfer(II) und N,N’-Ethylenbis(1-iminomethyl-2-naphtholato)nickel(II) Acta Crystallographica B. 1980;36:1209-1211. DOI: 10.1107/S056774088000564X
  8. 8. Karakas A, Elmali A, Unver H, Kara H, Yahsi Y. Synthesis, Structure, Spectroscopic Studies and ab-initio Calculations on First Hyperpolarizabilities of N,N’-Bis(2-hydroxy-1-naphthylmethylidene)-1-methyl-1,2-diaminoethane-N,N’,O,O’-copper(II). Zeitschrift für Naturforschung B. 2006;61:968-974
  9. 9. Li F, Mei C, Tao R. Henan Daxue Xuebao. Ziran Kexueban. 2006;36:32
  10. 10. Biswas S, Dutta A, Dolai M, Debnath M, Jana AD, Ali M. Copper(II) induced oxidative modification and complexation of a schiff base ligand: synthesis, crystal structure, catalytic oxidation of aromatic hydrocarbons and DFT calculation. RSC Advances. 2014;4:34248-34256. DOI: 10.1039/C4RA06078D
  11. 11. Xie QF, Chen YM, Huang ML. {4, 4′-Dibromo-2, 2′-[ethane-1, 2-diylbis (nitrilomethylidyne)] diphenolato} copper (II). Acta Crystallographica E. 2009;65:m903-m903. https://doi.org/10.1107/S1600536809024015
  12. 12. Clegg W, Harrington RW. CCDC ANEMAJ (Private Communication)
  13. 13. Rigamonti L, Demartin F, Forni A, Righetto S, Pasini A. Copper(II) complexes of salen analogues with two differently substituted (push-pull) salicylaldehyde moieties. A study on the modulation of electronic asymmetry and nonlinear optical properties. Inorganic Chemistry. 2006;45:10976-10989. DOI: 10.1021/ic0613513
  14. 14. Assey G, Butcher RJ, Gultneh Y. Acta Crystallographica E. {3,3′,5,5′-Tetramethoxy-2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}copper(II)2010;66:m653-m653. https://doi.org/10.1107/S1600536810017137
  15. 15. Arici C, Ercan F, Atakol O, Cakirer O. Aqua[N,N’-bis(salicylidene)-1,3-propanediaminato]copper(II)Acta Crystallographica C. 1999;55:1654-1655. DOI: 10.1107/S010827019900894X
  16. 16. Akhtar F, Drew MGB. Structures of N,N’-propylenebis[(2-hydroxy-1-naphthyl)methaniminato]nickel(II) and N,N’-propylenebis[(2-hydroxy-1-naphthyl)methaniminato]copper(II)–0.5-dimethyl sulphoxide. Acta Crystallographica B. 1982;38:1149-1154. https://doi.org/10.1107/S0567740882005184
  17. 17. Li XW, Xue LW, Zhang CX. Synthesis, X-Ray Structures, and Antimicrobial Activities of Nickel(II) and Copper(II) Complexes With Tetradentate Schiff Bases. Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry. 2015;45:512-515. https://doi.org/10.1080/15533174.2013.841217
  18. 18. Kitajima N, Whang K, Moro-oka K, Uchida A, Sasada Y. Oxidations of primary alcohols with a copper(II) complex as a possible galactose oxidase model. Journal of the Chemical Society, Chemical Communications. 1986:1504-1505. DOI: 10.1039/C39860001504
  19. 19. Chen BH, Yao HH, Huang WT, Chattopadhyay P, Lo JM, Lu TH. Syntheses and molecular structures of three Cu(II) complexes with tetradentate imine-phenols. Solid State Sciences. 1999;1:119-131. https://doi.org/10.1016/S1293-2558(00)80069-2
  20. 20. Elmali A, Zeyrek CT, Elerman Y, Svoboda I. [N,N′-Bis(5-bromosalicylidene)-1,3-diaminopropane]nickel(II) and [N,N′-bis(5-chlorosalicylidene)-1,3-diaminopropane]copper(II). Acta Crystallographica C. 2000;56:1302-1304. https://doi.org/10.1107/S0108270100010428
  21. 21. Wang X. Aqua{6,6-dimethoxy-2,2′-[propane-1,3-diylbis(nitrilomethylidyne)]diphenolato-κ4O,N,N′,O′}copper(II) acetonitrile solvate. Acta Crystallographica E. 2009;65:m1658-m1658. DOI: 10.1107/S1600536809049137
  22. 22. Habibi MH, Mokhtari R, Harrington RW, Clegg W. [N,N′-Bis(6-methoxysalicylidene)-1,3-diaminopropane]copper(II). Acta Crystallographica E. 2007;63:m1998-m1998. https://doi.org/10.1107/S1600536807030723
  23. 23. Habibi MH, Harrington RW. CCDC ANEMOX (Private Communication)
  24. 24. Odabasoglu M, Arslan F, Olmez H, Buyukgungor O. Synthesis, crystal structures and spectral characterization of trans-bisaquabis(o-vanillinato)copper(II), cis-aquabis(o-vanillinato)copper(II) and aqua[bis(o-vanillinato)-1,2-ethylenediimin]copper(II). Dyes and Pigments. 2007;75:507-515. https://doi.org/10.1016/j.dyepig.2006.06.033
  25. 25. Tsuda E, Mitsumoto Y, Takakura K, Sunaga N, Akitsu T, Konomi T, et al. Electrochemical tuning by polarized UV light induced molecular orientation of chiral salen-type Mn(II) and Co(II) complexes in an albumin matrix. Journal of Chemistry and Chemical Engineering. 2016;2:53-59. DOI: 10.17265/1934-7375/2016.02.001
  26. 26. Hayashi T, Akitsu T. Fluorescence, UV-vis, and CD Spectroscopic Study on Docking of Chiral Salen-Type Zn(II) Complexes and Lysozyme and HSA Proteins. Threonine: Food Sources, Functions and Health Benefits. NY, USA: Nova Science Publishers Inc.; 2015. ISBN:978-1634825542
  27. 27. Akitsu T, Yamazaki A. Semiempirical molecular orbital calculations for 3d-4f complexes towards artificial metalloproteins. International Journal of Pharma Sciences and Scientific Research. 2017;3:53-54. DOI: 10.25141/2471-6782-2017-2.0049
  28. 28. Akitsu T, Hiratsuka T, Shibata H. Chiroptical Properties of 3d-4f Chiral Schiff Base Magnetic Complexes. Magnets: Types, Uses and Safety. NY, USA: Nova Science Publishers, Inc.; 2012. ISBN: 978-1614702511
  29. 29. Hiratsuka T, Shibata H, Akitsu T. Structures and Properties of 3d-4f and 3d Chiral Schiff base Complexes. Crystallography: Research, Technology and Applications. NY, USA: Nova Science Publishers, Inc.; 2012. ISBN: 978-1620815748
  30. 30. Shibata H, Hiratsuka T, Hayashi T, Akitsu T. Structures and Electronic Properties of Photophysical Chiral Schiff Base 3d-4f Binuclear Complexes. Integrating Approach to Photofunctional Hybrid Materials for Energy and the Environment. NY, USA: Nova Science Publishers, Inc.; 2013. ISBN: 978-1624176388
  31. 31. Hayashi T, Shibata H, Orita S, Akitsu T. Variety of structures of binuclear chiral Schiff base Ce(III)/Pr(III)/Lu(III)-Ni(II)/Cu(II)/Zn(II) complexes. European Chemical Bulletin. 2013;2:49-57. DOI: 10.17628/ECB.2013.2.49
  32. 32. Orita S, Akitsu A. Variety of crystal structures of chiral Schiff base Lu(III)-Ni(II)/Cu(II)/Zn(II) and their related complexes. Open Chemistry Journal. 2014;1:1-14. DOI: 10.2174/1874842201401010001

Written By

Takashiro Akitsu

Published: January 11th, 2019