title: Halochromic coordination polymers based on a triarylmethane dye for reversible detection of acids.
abstract: Chromeazurol B (Na2HL) is a pH-sensitive (halochromic) dye based on a hydroxytriarylmethane core and two carboxylate functional groups, which makes it suitable for the synthesis of coordination polymers. Two new coordination polymers [NaZn4(H2O)3(L)3]·3THF·3H2O (1) and [Zn3(H2O)3(μ2-OH2)(μ3-OH)(HL)2(H2L)]·2THF·3H2O (2) incorporating Chromeazurol B linkers have been prepared and characterised. The structure of 1 comprises pentanuclear heterometallic {Zn4Na} nodes linked by six L3-anions to give a layered structure with a honeycomb topology. 2 crystallizes as a double-chain ribbon (ladder) structure with two types of metal node: a mononuclear Zn(ii) cation and tetranuclear {Zn(ii)}4cluster. Chromeazurol B anions link each tetranuclear cluster to four individual Zn(ii) cations and each Zn(ii) cation with four tetranuclear clusters. Both compounds show pH-sensitivity in water solution which can be observed visually, giving the first example of a halochromic coordination polymer. The halochromic properties of 1 towards HCl vapors were systematically investigated. As-synthesized violet-grey 1 reversibly changes color from orange to pink in the presence of vapors of 2 M and 7 M HCl, respectively. The coordination of the Chromeazurol B anion at each color stage was examined by diffuse reflectance spectroscopy and FT-IR measurements. The remarkable stability of 1 to acid and the observed reversible and reproducible color changes provide a new design for multifunctional sensor materials.
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave., 3, Novosibirsk, 630090, Russian Federation. dan@niic.nsc.ru and Novosibirsk State University, Pirogov str., 2, Novosibirsk, 630090, Russian Federation.
authors.forename: Marina S
authors.initials: MS
authors.lastname: Zavakhina
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave., 3, Novosibirsk, 630090, Russian Federation. dan@niic.nsc.ru.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Yushina
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave., 3, Novosibirsk, 630090, Russian Federation. dan@niic.nsc.ru and Novosibirsk State University, Pirogov str., 2, Novosibirsk, 630090, Russian Federation.
authors.forename: Denis G
authors.initials: DG
authors.lastname: Samsonenko
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave., 3, Novosibirsk, 630090, Russian Federation. dan@niic.nsc.ru and Novosibirsk State University, Pirogov str., 2, Novosibirsk, 630090, Russian Federation.
authors.forename: Danil N
authors.initials: DN
authors.lastname: Dybtsev
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave., 3, Novosibirsk, 630090, Russian Federation. dan@niic.nsc.ru and Novosibirsk State University, Pirogov str., 2, Novosibirsk, 630090, Russian Federation.
authors.forename: Vladimir P
authors.initials: VP
authors.lastname: Fedin
authors.affiliation: School of Chemistry, University of Nottingham, NG7 2RD Nottingham, UK.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Argent
authors.affiliation: School of Chemistry, University of Nottingham, NG7 2RD Nottingham, UK.
authors.forename: Alexander J
authors.identifier: http://orcid.org/0000-0003-2257-8332
authors.initials: AJ
authors.lastname: Blake
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Acad. Lavrentiev Ave., 3, Novosibirsk, 630090, Russian Federation. dan@niic.nsc.ru and School of Chemistry, University of Manchester, M13 9PL Manchester, UK.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0001-6992-0700
authors.initials: M
authors.lastname: Schröder