title: Dimensionality control of vapochromic hydrogen-bonded proton-transfer assemblies composed of a bis(hydrazone)iron(II) complex.
abstract: We describe the novel synthesis of a bis(hydrazone)iron(II) complex in protonated [Fe(Hpbph)(2)]Cl(2) (1) and deprotonated [Fe(pbph)(2)] (2) forms and several hydrogen-bonded proton-transfer (HBPT) assemblies having different dimensionalities of hydrogen-bonded network structures, [Fe(Hpbph)(2)](CA)·2CH(3)OH (3), [Fe(Hpbph)(2)](HCA)(2)·2THF (4), and [Fe(Hpbph)(2)](CA)(H(2)CA)(2)·2CH(3)CN (5) (Hpbph = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone), consisting of a deprotonated Fe(II)-hydrazone complex (2) as a proton acceptor (A) and chloranilic acid (H(2)CA) as a proton donor (D). The deprotonated complex 2 exhibited two-step reversible protonation reactions to form the double-protonated form 1, and the acid-dissociation constants were determined to be 7.6 and 10.3 in methanol solution. Utilizing this proton-accepting ability of 2, we succeeded in synthesizing HBPT assemblies 3, 4, and 5 from the reactions in CH(3)OH, THF, and CH(3)CN, respectively, with the same D/A ratio of H(2)CA/[Fe(pbph)(2)] = 10:1. These assemblies were found to have one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) hydrogen-bonded networks with D/A ratios of 1:1, 2:1, and 3:1 for 3, 4, and 5, respectively. In 3, a 1-D hydrogen-bonded chain composed of the alternate arrangement of [Fe(Hpbph)(2)](2+) and CA(2-), {···[Fe(Hpbph)(2)](2+)···CA(2-)···}(∞), was surrounded by solvated methanol molecules to form isolated 1-D hydrogen-bonded chains. In the HBPT assembly 4, a 2-D hydrogen-bonded sheet was formed from two types of hydrogen-bonded chains, {···[Fe(Hpbph)(2)](2+)···HCA(-)···HCA(-)···}(∞) and {···HCA(-)···HCA(-)···}(∞), and solvated THF molecules did not form any hydrogen bonds. In 5, two orthogonal hydrogen-bonded chains constructed from the neutral chloranilic acid molecules, {···CA(2-)···2(H(2)CA)···}(∞), were formed in addition to the 1-D hydrogen-bonded chain similar to that in 3, resulting in the formation of a rigid 3-D hydrogen-bonded network structure. By controlling the dimensionality of the hydrogen bond network, we found that the 2-D HBPT assembly 4 is sufficiently flexible to exhibit interesting vapochromic behavior in response to various organic vapors.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, North-10 West-8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Mee
authors.initials: M
authors.lastname: Chang
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Nakajima
authors.forename: Ho-Chol
authors.initials: HC
authors.lastname: Chang
authors.forename: Masako
authors.initials: M
authors.lastname: Kato
mesh_terms: D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006835:Hydrazones / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D033362:Powder Diffraction; D011522:Protons; D014835:Volatilization
chemical_list: D005296:Ferrous Compounds; D006835:Hydrazones; D011522:Protons