Metal Complexes of π-Expanded Ligands (4): Synthesis and Characterizations of Copper(II) Complexes with a Schiff Base Ligand Derived from Pyrene
Main Article Content
Abstract
An innovative π-expanded ligand derived from salicylaldimine ligand representing pyrene ring as a substitute for benzene ring was synthesized in 5 steps from commercially available pyrene. This unique bidentate ligand (1) was coordinated to Cu(II) metal centre for affording complex 2, which was characterized by IR, elemental, X-ray diffraction analyses, and magnetic susceptibility. Its coordination geometry is a trans-square plane with an obvious stair-step structure which is formed by two pyrene moieties and the coordination plane (CuN2O2). In addition, the dihedral angle between the coordination plane and the pyrene ring is 34.9o and the plane of seven carbon atoms of the long alkyl chains were arranged nearly parallel to the pyrene rings. The electronic properties of this novel complex 2 were examined via cyclic voltammetry and absorption spectroscopy to show the narrower HOMO-LUMO gap than those of the complex 4. Moreover, the particular behavior of both complexes 2 and 4 was investigated through DFT studies.
Keywords:
Coordination chemistry, Copper, Pyrene, π-Expanded ligand, Salicylaldimine.
References
[1] D.J. Jones, V.C. Gibson, S.M. Green, P.J. Maddox, A.J.P. White, D.J. Williams, Discovery and optimization of new chromium catalysts for ethylene oligomerization and polymerization aided by high-throughput screening, J. Am. Chem. Soc. 127 (2005) 11037-11046. https://doi.org/10. 1021/ja0518171.
[2] T. Wiedemann, G. Voit, A. Tchernook, P. Roesle, I.G. Schnetmann, S. Mecking, Monofunctional hyperbranched ethylene oligomers, J. Am. Chem. Soc. 136 (2014) 2078-2085. https://doi.org/10.10 21/ja411945n.
[3] N. Hoshino, Liquid crystal properties of metal–salicylaldimine complexes.: Chemical modifications towards lower symmetry, Coord. Chem. Rev. 174 (1998) 77-108. https://doi.org/10.1016/S0010-8545 (98)00129-5.
[4] C.K. Lai, C.H. Chang, C.H. Tsai, Liquid crystalline properties of bis (salicylaldiminato) copper(II) complexes: the first columnar discotics derived from salicylaldimine Schiff bases, J. Mater. Chem. 8 (1998) 599-602. https://doi.org/10.1039/A707091H.
[5] P. Wang, Z. Hong, Z. Xie, S. Tong, O. Wong, C.S. Lee, N. Wong, L. Hung, S. Lee, A bis-salicylaldiminato Schiff base and its zinc complex as new highly fluorescent red dopants for high performance organic electroluminescence devices, Chem. Commun. (2003) 1664-1665. https://doi.org/10.1039/B303591C.
[6] C.C. Kwok, S C. Yu, I.H.T. Sham, C.M. Che, Self-assembled zinc(ii) Schiff basepolymers for applications in polymer light-emitting devices, Chem. Commun. (2004) 2758-2759. https://doi. org/10.1039/B412762E.
[7] M. Calvin, K.W. Wilson, Stability of Chelate Compounds, J. Am. Chem. Soc. 67 (1945) 2003-2007. https://doi.org/10.1021/ja01227a043.
[8] M. Calvin, N.C. Melchior, Stability of chelate compounds. IV. Effect of the metal ion, J. Am. Chem. Soc. 70 (1948) 3270-3273. https://doi.org/ 10.1021/ja01190a020.
[9] T.M.F. Duarte, K. Müllen, Pyrene-based materials for organic electronics, Chem. Rev. 111 (2011) 7260-7314. https://doi.org/10.1021/cr100428a.
[10] M. Shiotsuka, Y. Okaue, N. Matsumoto, H. Okawa, T. Isobe, Crystal structures and single-crystal electron spin resonance spectra of π–π type molecular complexes of bis(1-methyliminomethyl -2-naphtholato)copper(II), J. Chem. Soc., Dalton Trans. (1994) 2065-2070. https://doi.org/10.1039/ DT9940002065.
[11] K. Nishijima, T. Nozaki, H. Miyasaka, G. Mago, N. Matsumoto, The 1:2 and 1:4 π-π type molecular adducts of bis (N-alkyl-2-oxy-4-(1-naphthoyloxy) benzaldiminato) copper (II) and 1,3,5-trinitrobenzene, Inorganica Chimica Acta 234 (1995)131-137. https://doi.org/10.1016/0020-1693(95)04490-Z.
[12] C.W. Tang, Two-layer organic photovoltaic cell, Applied Physics Letters 48 (1986) 183-185. Http://adsabs.harvard.edu/abs/1986ApPhL..48..183T.
[13] M. Hiramoto, M. Kubo, Y. Shinmura, N. Ishiyama, T. Kaji, K. Sakai, T. Ohno, M. Izaki, Bandgap science for organic solar cells, Electronics 3 (2014) 351-380. https://doi.org/10. 3390/electronics3020351.
[14] W. Leslie, R.A. Poole, P.R. Murray, L.J. Yellowlees, A. Beeby, J.A.G. Williams, Near infra-red luminescence from bis-terpyridyl iridium(III) complexes incorporating electron-rich pendants, Polyhedron 23 (2004) 2769-2777. https: //doi.org/10.1016/j.poly.2004.08.009.
[15] S. Faulkner, M.C. Carrié, S.J.A. Pope, J. Squire, A. Beeby, P.G. Sammes, Dalton Trans. (2004) 1405-1409. https://doi.org/10.1039/B401302F.
[16] S. Roy, S. Roy, S. Saha, R. Majumdar, R.R. Dighe, E.D. Jemmis, A.R. Chakravart, Cobalt(II) complexes of terpyridine bases as photochemotherapeutic agents showing cellular uptake and photocytotoxicity in visible light, Dalton Trans. 40 (2011) 1233. https://doi.org/10.1039/C0DT00223B.
[17] W. Wu, J. Sun, S. Ji, W. Wu, J. Zhao, H. Guo, Tuning the emissive triplet excited states of platinum(ii) Schiff base complexes with pyrene, and application for luminescent oxygen sensing and triplet–triplet-annihilation based upconversions, Dalton Trans. 40 (2011) 11550-11561. https://doi. org/10.1039/C1DT11001B.
[18] N.M. Cox, L.P. Harding, J.E. Jones, S.J.A. Pope, C.R. Rice, H. Adams, Probing solution behaviour of metallosupramolecular complexes using pyrene fluorescence, Dalton Trans. 41 (2012) 1568. https://doi.org/10.1039/C1DT11831E.
[19] J. Zhao, S. Ji, W. Wu, W. Wu, H. Guo, J. Sun, H. Sun, Y. Liu, Q. Li, L. Huang, Transition metal complexes with strong absorption of visible light and long-lived triplet excited states: from molecular design to applications, RSC Advances 2 (2012) 1712-1728. https://doi.org/10.1039/C1 RA00665G.
[20] R. Liu, N. Dandu, Y. Li, S. Kilina, W. Sun, Synthesis, photophysics and reverse saturable absorption of bipyridyl platinum(II) bis(arylfluorenylacetylide) complexes, Dalton Trans. 42 (2013) 4398-4409. https://doi.org/10.1039/C2DT32153J.
[21] A.S. Ionkin, William J. Marshall, Brian M. Fish, Synthesis and structural characterization of a series of novel polyaromatic ligands containing pyrene and related biscyclometalated iridium(III) complexes, Organometallics 25 (2006) 1461-1471. https://doi.org/10.1021/om0510775.
[22] W.Y. Heng, J. Hu, J.H.K. Yip, Attaching gold and platinum to the rim of pyrene: A synthetic and spectroscopic study, Organometallics 26 (2007) 6760. https://doi.org/10.1021/om700716p.
[23] Y.F. Han, H. Li, P. Hu, G.X. Jin, Alkyne insertion induced regiospecific C−H activation with [Cp*MCl2]2 (M = Ir, Rh), Organometallics 30 (2011) 905-911. https://doi.org/10.1021/om101064v.
[24] R.M. Edkins, K. Fucke, M.J.G. Peach, A.G. Crawford, T.B. Marder, A. Beeby, Syntheses, structures, and comparison of the photophysical properties of cyclometalated iridium complexes containing the isomeric 1- and 2-(2-pyridyl) pyrene ligands, Inorg. Chem. 52 (2013) 9842-9860. https://doi.org/10.1021/om101064v.
[25] X. Sun, Y.-W. Wang, Y. Peng, A selective and ratiometric bifunctional fluorescent probe for Al3+ ion and proton, Org. Lett. 14 (2012) 3420-3423. https://doi.org/10.1021/ol301390g.
[26] Luong Xuan Dien, Ken-ichi Yamashita, Motoko S. Asano, Ken-ichi Sugiura, Synthesis of a pyrene-based π-expanded ligand and the corresponding platinum(II) complex, Bis[2-[(octylimino) methyl] -1-pyrenolato-N,O] platinum(II), Inorganica Chimica Acta, 432 (2015) 103-108. https://doi.org/10.1016/ j.ica.2015.03.038.
[27] Luong Xuan Dien, Ken-ichi Yamashita, Ken-ichi Sugiura, Metal Complexes of π-Expanded Ligands (2): Synthesis and characterizations of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] palladium(II) and the stabilized vacant dx2-y2 orbital, Polyhedron, 102 (2015) 69-74. https://doi. org/10.1016/j.poly.2015.07.043.
[28] Luong Xuan Dien, Nguyen Xuan Truong, Ngo Duc Quan, Ken-ichi Yamashita, Ken-ichi Sugiura, Syntheses and structures of Ni(II) complexes containing 2 alkyliminomethyl pyrene ligands, VNU Journal of Science 34 (4) (2018) 16-20. https://doi.org/10.25073/2588-1140/vnunst.4809.
[29] Luong Xuan Dien, Nguyen Kim Nga, Nguyen Xuan Truong, Ken-ichi Yamashita and Ken-ichi Sugiura, Metal Complexes of π-Expanded Ligands (3): Synthesis and characterizations of tris[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(III), VNU Journal of Science 35 (2) (2019) 98-105. https://doi.org/10.25073/2588-1140/vnunst. 4898.
[30] P. Demerseman, J. Einhorn, J.F. Gourvest, R. Royer, Synthèse d'analogues furanniques du benzo[a]pyrene, J. Heterocycl. Chem. 22 (1985) 39-43. https://doi.org/10.1002/jhet.5570220110.
[31] L.Z. Zhang, P.Y. Bu, L.J. Wang, P. Cheng, Bis(N-octylsalicylideniminato-N,O)copper(II), Acta Cryst. C57 (2001) 1166-1167. http://scripts.iucr. org/cgi-bin/paper?-S0108270101013154.
[32] L. Sacconi, M. Ciampolini, 45. Pseudo-tetrahedral structure of some α-branched copper(II) chelates with Schiff bases, J. Chem. Soc., 1964, 276-280. https://doi.org/10.1039/JR9640000276.
[33] P. Teyssie, J.J. Charette, Physico-chemical properties of co-ordinating compounds—III: Infrared spectra of N-salicyclidenealkylamines and their chelates, Spectrochim. Acta 19 (1963) 1407-1423. https://doi.org/10.1016/0371-1951(63) 80003-X.
[34] J.E. Kovacic, The C-N stretching frequency in the infrared spectra of Schiff's base complexes-I. Copper complexes of salicylidene anilines, Spectrochim. Acta, Part A 23 (1967) 183-187. https://doi.org/10.1016/0584-8539(67)80219-8.
[35] N.V. Tverdova, N.I. Giricheva, G.V. Girichev, N.P. Kuz'mina, O.V. Kotova, A.V. Zakharov, IR Spectra of N,N’-Ethylene-Bis(salicylaldiminates) and N,N-ethylene- Bis(acetylacetoniminates) of Ni(II), Cu(II), and Zn(II), Russ. J. Phys. Chem. A 83 (2009) 2255-2265. https://doi.org/10.1134/ S0036024409130135.
[36] J.D. Goulden, The Infrared spectra of quaternary methiodides of NN-disubstituted thioamides, J. Chem. Soc. (1953) 997-998. https://doi.org/10. 1039/JR9530000996.
[37] P.E. Hansen, A. Berg, Infrared Spectra of Pyrene Derivatives. Relation to the Substitution Pattern., Acta Chem. Scand., Ser. B35 (1981)131-137. http://actachemscand.org/pdf/acta_vol_35b_p0131-0137.pdf.
[38] Ian Fleming, Molecular Orbitals and Organic Chemical Reactions, Wiley, United Kingdom, 2009, pp 31.
[39] D. Hall, R.H. Sumner, T.N. Waters, The colour isomerism and structure of copper co-ordination compounds. Part XVIII. The crystal structure of bis-(N-n-butylsalicylaldiminato)-copper(II), J. Chem. Soc. A (1969) 420-422. https://doi.org/10.1039/ J19690000420.
[40] G.M. Sheldrick, SHELXL-97: Program for the Solution and Refinement of Crystal Structures; University of Göttingen: Göttingen, Germany, 1997.
[41] P.J. Hay, W.R. Wadt, Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg, J. Chem. Phys. 82 (1985) 299. https://doi.org/10.1063/1. 448799.
[42] M.J. Frisch; et al. Gaussian 09, Revision A.1; Wallingford, CT, 2009.
[43] E. Safaei, M.M. Kabir, A. Wojtczak, Z. Jaglicic, A. Kozakiewicz, Y. I. Lee, Synthesis, crystal structure, magnetic and redox properties of copper(II) complexes of N-alkyl(aryl) tBu-salicylaldimines, Inorganica Chimica Acta 366 (2011) 275-282. https://doi.org/10.1016/j.ica.2010. 11.017.
[44] A. Ríos-Escudero, M. Villagrán, F. Caruso, J.P. Muena, E. Spodine, D. Venegas-Yazigi, L. Massa, L.J. Todaro, J. H. Zagal, G.I. Cárdenas-Jirón, M. Páez, J. Costamagna, Electrocatalytic reduction of carbon dioxide induced by bis(N-R-2-hydroxy-1-naphthaldiminato)-copper(II) (R = n-octyl, n-dodecyl): Magnetic and theoretical studies and the X-ray structure of bis(N-n-octyl-2-hydroxy-1-naphthaldiminato)-copper(II), Inorganica Chimica Acta 359 (2006) 3947-3953. https://doi.org/10. 1016/j.ica.2006.04.027.
[2] T. Wiedemann, G. Voit, A. Tchernook, P. Roesle, I.G. Schnetmann, S. Mecking, Monofunctional hyperbranched ethylene oligomers, J. Am. Chem. Soc. 136 (2014) 2078-2085. https://doi.org/10.10 21/ja411945n.
[3] N. Hoshino, Liquid crystal properties of metal–salicylaldimine complexes.: Chemical modifications towards lower symmetry, Coord. Chem. Rev. 174 (1998) 77-108. https://doi.org/10.1016/S0010-8545 (98)00129-5.
[4] C.K. Lai, C.H. Chang, C.H. Tsai, Liquid crystalline properties of bis (salicylaldiminato) copper(II) complexes: the first columnar discotics derived from salicylaldimine Schiff bases, J. Mater. Chem. 8 (1998) 599-602. https://doi.org/10.1039/A707091H.
[5] P. Wang, Z. Hong, Z. Xie, S. Tong, O. Wong, C.S. Lee, N. Wong, L. Hung, S. Lee, A bis-salicylaldiminato Schiff base and its zinc complex as new highly fluorescent red dopants for high performance organic electroluminescence devices, Chem. Commun. (2003) 1664-1665. https://doi.org/10.1039/B303591C.
[6] C.C. Kwok, S C. Yu, I.H.T. Sham, C.M. Che, Self-assembled zinc(ii) Schiff basepolymers for applications in polymer light-emitting devices, Chem. Commun. (2004) 2758-2759. https://doi. org/10.1039/B412762E.
[7] M. Calvin, K.W. Wilson, Stability of Chelate Compounds, J. Am. Chem. Soc. 67 (1945) 2003-2007. https://doi.org/10.1021/ja01227a043.
[8] M. Calvin, N.C. Melchior, Stability of chelate compounds. IV. Effect of the metal ion, J. Am. Chem. Soc. 70 (1948) 3270-3273. https://doi.org/ 10.1021/ja01190a020.
[9] T.M.F. Duarte, K. Müllen, Pyrene-based materials for organic electronics, Chem. Rev. 111 (2011) 7260-7314. https://doi.org/10.1021/cr100428a.
[10] M. Shiotsuka, Y. Okaue, N. Matsumoto, H. Okawa, T. Isobe, Crystal structures and single-crystal electron spin resonance spectra of π–π type molecular complexes of bis(1-methyliminomethyl -2-naphtholato)copper(II), J. Chem. Soc., Dalton Trans. (1994) 2065-2070. https://doi.org/10.1039/ DT9940002065.
[11] K. Nishijima, T. Nozaki, H. Miyasaka, G. Mago, N. Matsumoto, The 1:2 and 1:4 π-π type molecular adducts of bis (N-alkyl-2-oxy-4-(1-naphthoyloxy) benzaldiminato) copper (II) and 1,3,5-trinitrobenzene, Inorganica Chimica Acta 234 (1995)131-137. https://doi.org/10.1016/0020-1693(95)04490-Z.
[12] C.W. Tang, Two-layer organic photovoltaic cell, Applied Physics Letters 48 (1986) 183-185. Http://adsabs.harvard.edu/abs/1986ApPhL..48..183T.
[13] M. Hiramoto, M. Kubo, Y. Shinmura, N. Ishiyama, T. Kaji, K. Sakai, T. Ohno, M. Izaki, Bandgap science for organic solar cells, Electronics 3 (2014) 351-380. https://doi.org/10. 3390/electronics3020351.
[14] W. Leslie, R.A. Poole, P.R. Murray, L.J. Yellowlees, A. Beeby, J.A.G. Williams, Near infra-red luminescence from bis-terpyridyl iridium(III) complexes incorporating electron-rich pendants, Polyhedron 23 (2004) 2769-2777. https: //doi.org/10.1016/j.poly.2004.08.009.
[15] S. Faulkner, M.C. Carrié, S.J.A. Pope, J. Squire, A. Beeby, P.G. Sammes, Dalton Trans. (2004) 1405-1409. https://doi.org/10.1039/B401302F.
[16] S. Roy, S. Roy, S. Saha, R. Majumdar, R.R. Dighe, E.D. Jemmis, A.R. Chakravart, Cobalt(II) complexes of terpyridine bases as photochemotherapeutic agents showing cellular uptake and photocytotoxicity in visible light, Dalton Trans. 40 (2011) 1233. https://doi.org/10.1039/C0DT00223B.
[17] W. Wu, J. Sun, S. Ji, W. Wu, J. Zhao, H. Guo, Tuning the emissive triplet excited states of platinum(ii) Schiff base complexes with pyrene, and application for luminescent oxygen sensing and triplet–triplet-annihilation based upconversions, Dalton Trans. 40 (2011) 11550-11561. https://doi. org/10.1039/C1DT11001B.
[18] N.M. Cox, L.P. Harding, J.E. Jones, S.J.A. Pope, C.R. Rice, H. Adams, Probing solution behaviour of metallosupramolecular complexes using pyrene fluorescence, Dalton Trans. 41 (2012) 1568. https://doi.org/10.1039/C1DT11831E.
[19] J. Zhao, S. Ji, W. Wu, W. Wu, H. Guo, J. Sun, H. Sun, Y. Liu, Q. Li, L. Huang, Transition metal complexes with strong absorption of visible light and long-lived triplet excited states: from molecular design to applications, RSC Advances 2 (2012) 1712-1728. https://doi.org/10.1039/C1 RA00665G.
[20] R. Liu, N. Dandu, Y. Li, S. Kilina, W. Sun, Synthesis, photophysics and reverse saturable absorption of bipyridyl platinum(II) bis(arylfluorenylacetylide) complexes, Dalton Trans. 42 (2013) 4398-4409. https://doi.org/10.1039/C2DT32153J.
[21] A.S. Ionkin, William J. Marshall, Brian M. Fish, Synthesis and structural characterization of a series of novel polyaromatic ligands containing pyrene and related biscyclometalated iridium(III) complexes, Organometallics 25 (2006) 1461-1471. https://doi.org/10.1021/om0510775.
[22] W.Y. Heng, J. Hu, J.H.K. Yip, Attaching gold and platinum to the rim of pyrene: A synthetic and spectroscopic study, Organometallics 26 (2007) 6760. https://doi.org/10.1021/om700716p.
[23] Y.F. Han, H. Li, P. Hu, G.X. Jin, Alkyne insertion induced regiospecific C−H activation with [Cp*MCl2]2 (M = Ir, Rh), Organometallics 30 (2011) 905-911. https://doi.org/10.1021/om101064v.
[24] R.M. Edkins, K. Fucke, M.J.G. Peach, A.G. Crawford, T.B. Marder, A. Beeby, Syntheses, structures, and comparison of the photophysical properties of cyclometalated iridium complexes containing the isomeric 1- and 2-(2-pyridyl) pyrene ligands, Inorg. Chem. 52 (2013) 9842-9860. https://doi.org/10.1021/om101064v.
[25] X. Sun, Y.-W. Wang, Y. Peng, A selective and ratiometric bifunctional fluorescent probe for Al3+ ion and proton, Org. Lett. 14 (2012) 3420-3423. https://doi.org/10.1021/ol301390g.
[26] Luong Xuan Dien, Ken-ichi Yamashita, Motoko S. Asano, Ken-ichi Sugiura, Synthesis of a pyrene-based π-expanded ligand and the corresponding platinum(II) complex, Bis[2-[(octylimino) methyl] -1-pyrenolato-N,O] platinum(II), Inorganica Chimica Acta, 432 (2015) 103-108. https://doi.org/10.1016/ j.ica.2015.03.038.
[27] Luong Xuan Dien, Ken-ichi Yamashita, Ken-ichi Sugiura, Metal Complexes of π-Expanded Ligands (2): Synthesis and characterizations of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] palladium(II) and the stabilized vacant dx2-y2 orbital, Polyhedron, 102 (2015) 69-74. https://doi. org/10.1016/j.poly.2015.07.043.
[28] Luong Xuan Dien, Nguyen Xuan Truong, Ngo Duc Quan, Ken-ichi Yamashita, Ken-ichi Sugiura, Syntheses and structures of Ni(II) complexes containing 2 alkyliminomethyl pyrene ligands, VNU Journal of Science 34 (4) (2018) 16-20. https://doi.org/10.25073/2588-1140/vnunst.4809.
[29] Luong Xuan Dien, Nguyen Kim Nga, Nguyen Xuan Truong, Ken-ichi Yamashita and Ken-ichi Sugiura, Metal Complexes of π-Expanded Ligands (3): Synthesis and characterizations of tris[2-[(octylimino)methyl]-1-pyrenolato-N,O] cobalt(III), VNU Journal of Science 35 (2) (2019) 98-105. https://doi.org/10.25073/2588-1140/vnunst. 4898.
[30] P. Demerseman, J. Einhorn, J.F. Gourvest, R. Royer, Synthèse d'analogues furanniques du benzo[a]pyrene, J. Heterocycl. Chem. 22 (1985) 39-43. https://doi.org/10.1002/jhet.5570220110.
[31] L.Z. Zhang, P.Y. Bu, L.J. Wang, P. Cheng, Bis(N-octylsalicylideniminato-N,O)copper(II), Acta Cryst. C57 (2001) 1166-1167. http://scripts.iucr. org/cgi-bin/paper?-S0108270101013154.
[32] L. Sacconi, M. Ciampolini, 45. Pseudo-tetrahedral structure of some α-branched copper(II) chelates with Schiff bases, J. Chem. Soc., 1964, 276-280. https://doi.org/10.1039/JR9640000276.
[33] P. Teyssie, J.J. Charette, Physico-chemical properties of co-ordinating compounds—III: Infrared spectra of N-salicyclidenealkylamines and their chelates, Spectrochim. Acta 19 (1963) 1407-1423. https://doi.org/10.1016/0371-1951(63) 80003-X.
[34] J.E. Kovacic, The C-N stretching frequency in the infrared spectra of Schiff's base complexes-I. Copper complexes of salicylidene anilines, Spectrochim. Acta, Part A 23 (1967) 183-187. https://doi.org/10.1016/0584-8539(67)80219-8.
[35] N.V. Tverdova, N.I. Giricheva, G.V. Girichev, N.P. Kuz'mina, O.V. Kotova, A.V. Zakharov, IR Spectra of N,N’-Ethylene-Bis(salicylaldiminates) and N,N-ethylene- Bis(acetylacetoniminates) of Ni(II), Cu(II), and Zn(II), Russ. J. Phys. Chem. A 83 (2009) 2255-2265. https://doi.org/10.1134/ S0036024409130135.
[36] J.D. Goulden, The Infrared spectra of quaternary methiodides of NN-disubstituted thioamides, J. Chem. Soc. (1953) 997-998. https://doi.org/10. 1039/JR9530000996.
[37] P.E. Hansen, A. Berg, Infrared Spectra of Pyrene Derivatives. Relation to the Substitution Pattern., Acta Chem. Scand., Ser. B35 (1981)131-137. http://actachemscand.org/pdf/acta_vol_35b_p0131-0137.pdf.
[38] Ian Fleming, Molecular Orbitals and Organic Chemical Reactions, Wiley, United Kingdom, 2009, pp 31.
[39] D. Hall, R.H. Sumner, T.N. Waters, The colour isomerism and structure of copper co-ordination compounds. Part XVIII. The crystal structure of bis-(N-n-butylsalicylaldiminato)-copper(II), J. Chem. Soc. A (1969) 420-422. https://doi.org/10.1039/ J19690000420.
[40] G.M. Sheldrick, SHELXL-97: Program for the Solution and Refinement of Crystal Structures; University of Göttingen: Göttingen, Germany, 1997.
[41] P.J. Hay, W.R. Wadt, Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg, J. Chem. Phys. 82 (1985) 299. https://doi.org/10.1063/1. 448799.
[42] M.J. Frisch; et al. Gaussian 09, Revision A.1; Wallingford, CT, 2009.
[43] E. Safaei, M.M. Kabir, A. Wojtczak, Z. Jaglicic, A. Kozakiewicz, Y. I. Lee, Synthesis, crystal structure, magnetic and redox properties of copper(II) complexes of N-alkyl(aryl) tBu-salicylaldimines, Inorganica Chimica Acta 366 (2011) 275-282. https://doi.org/10.1016/j.ica.2010. 11.017.
[44] A. Ríos-Escudero, M. Villagrán, F. Caruso, J.P. Muena, E. Spodine, D. Venegas-Yazigi, L. Massa, L.J. Todaro, J. H. Zagal, G.I. Cárdenas-Jirón, M. Páez, J. Costamagna, Electrocatalytic reduction of carbon dioxide induced by bis(N-R-2-hydroxy-1-naphthaldiminato)-copper(II) (R = n-octyl, n-dodecyl): Magnetic and theoretical studies and the X-ray structure of bis(N-n-octyl-2-hydroxy-1-naphthaldiminato)-copper(II), Inorganica Chimica Acta 359 (2006) 3947-3953. https://doi.org/10. 1016/j.ica.2006.04.027.