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Neocuproine
Names
	Preferred IUPAC name 2,9-Dimethyl-1,10-phenanthroline
Identifiers
CAS Number	484-11-7 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:91222 ;
ChemSpider	58734 ;
ECHA InfoCard	100.006.911
EC Number	207-601-9;
PubChem CID	65237;
UNII	8E7D2SH3BV ;
CompTox Dashboard (EPA)	DTXSID5060065 ;
	InChI InChI=1S/C14H12N2/c1-9-3-5-11-7-8-12-6-4-10(2)16-14(12)13(11)15-9/h3-8H,1-2H3 Key: IYRGXJIJGHOCFS-UHFFFAOYSA-N ; InChI=1/C14H12N2/c1-9-3-5-11-7-8-12-6-4-10(2)16-14(12)13(11)15-9/h3-8H,1-2H3 Key: IYRGXJIJGHOCFS-UHFFFAOYAL;
	SMILES n1c3c(ccc1C)ccc2ccc(nc23)C;
Properties
Chemical formula	C14H12N2
Molar mass	208.264 g·mol−1
Appearance	Pale yellow solid
Melting point	162 to 164 °C (324 to 327 °F; 435 to 437 K)
Solubility in water	Slightly soluble
Solubility	Ethanol, Acetone, Ether, Benzene, Light Petroleum (slightly)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Neocuproine is a heterocyclic organic compound and chelating agent. Phenanthroline ligands were first published in the late 19th century, and the derivatives substituted at the 2 and 9 positions are among the most studied of the modified phenanthrolines.^[2]^[3]

Synthesis and structure

Neocuproine can be prepared by sequential Skraup reactions (Doebner-Miller reaction/condensation) of o-nitroaniline (2-Nitroaniline) with crotonaldehyde diacetate. An alternate synthesis involves the condensation of o-phenylenediamine, m-nitrobenzenesulphonate, and crotonaldehyde diacetate. This method gives higher yields but is less economical.^[1] Neocuproine crystallizes as a dihydrate and a hemihydrate.

Coordination chemistry

In the early 1930s, phenanthroline derivatives became known for their use as colorimetric indicators for many transition metals. Neocuproine proved to be highly selective for copper(I). The resulting complex, [Cu(neocuproine)₂]⁺ has a deep orange-red color.^[1] The properties of copper(I) neocuproine complexes have been widely studied, e.g. for the preparation of catenane and rotaxane complexes.^[4] The copper-catalyzed release of NO⁺ (nitrosonium) from S-Nitrosothiols is inhibited by neocuproine.^[5]

Relative to 1,10-phenanthroline, neocuproine bears steric bulk flanking the nitrogen donor sites. A major consequence is that complexes of the type [M(neocuproine)₃]ⁿ⁺ are disfavored, in contrast to the situation with phenanthroline ligands that lack substitution in the 2,9 positions.^[6] The ligand bathocuproine is similar to neocuproine, but has phenyl substituents at the 4,7-positions.

Other metals

Platinum forms the square planar complexes [PtX₂(2,9-dimethyl-1,10-phenanthroline)].^[7]

Neocuproine has also been discovered to have properties that cause fragmentation and disappearance of the melanin in adult zebrafish melanocytes. Those expressing eGFP also have been observed to lose eGFP fluorescence in the presence of neocuproine.^[8]

References

^ ^a ^b ^c O'Reilly, E. J.; Plowman, R. A. (1959). "Coordination Compounds of Substituted 1,10-Phenanthrolines and Related Dipyridyls". Australian Journal of Chemistry. 13 (1): 145–149. doi:10.1071/CH9600145.
^ M. K. Eggleston; P. E. Fanwick; A. J. Pallenberg; D. R. McMillin (1997). "A Twist on the Copper Center in the Crystal Structure of [Cu(dnpp)₂]PF₆ and the Charge-Transfer Excited State? (dnpp = 2,9-Dineopentyl-1,10-phenanthroline)". Inorganic Chemistry. 36 (18): 4007–4010. doi:10.1021/ic970135e.
^ Chandler, Christopher J.; Deady, Leslie W.; Reiss, James A. (1981). "Synthesis of some 2,9-Disubstituted-1,10-phenanthrolines". Journal of Heterocyclic Chemistry. 18 (3): 599–601. doi:10.1002/jhet.5570180332.
^ McCleverty, J; Meyer, T. J. "Phenanthroline Ligands" in Comprehensive Coordination Chemistry II, Vol. 1, 2004, p.25-39.
^ Al-Sa’doni, H.H.; Megson, I.L.; Bisland, S.; Butler, A.R.; Flitney, F.W. Neocuproine, A Selective Cu(I) Chelator, and the relaxation of rat vascular smooth muscle by S-nitrosothiols. British Journal of Pharmacology, 121(6), 1997, p.1047-1050. doi:10.1038/sj.bjp.0701218
^ Pallenberg, A. J.; Marschner, T. M.; Barnhart, D. M. (1997). "Phenanthroline complexes of the d¹⁰ Metals Nickel(0), Zinc(II) and Silver(I)—Comparison to Copper(I) Species". Polyhedron. 16 (16): 2711–2719. doi:10.1016/S0277-5387(97)00051-X.
^ Fanizzi, Francesco P.; Margiotta, Nicola; Lanfranchi, Maurizio; Tiripicchio, Antonio; Pacchioni, Gianfranco; Natile, Giovanni "A Molecular Tool for Measuring the Electron-Acceptor Ability of Ligands from Crystallographic Data" European Journal of Inorganic Chemistry volume 8, 2004, p.1705-1713. doi:10.1002/ejic.200300888
^ O’Reilly-Pol, Thomas; Johnson, Stephen L. "Neocuproine Ablates Melanocytes in Adult Zebrafish" Zebrafish 5(4). Mary Ann Liebert, Inc. 2008. doi:10.1089/zeb.2008.0540