title: Anion-π recognition between [M(CN)6]3-complexes and HAT(CN)6: structural matching and electronic charge density modification.
abstract: Hexacyanidometalates (M = FeIII, CoIII) and multisite anion receptor HAT(CN)6(1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile) recognize each other in acetonitrile solution and self-assemble into the novel molecular networks (PPh4)3[M(CN)6][HAT(CN)6] (M = Fe, 1; Co, 2) and (AsPh4)3[M(CN)6][HAT(CN)6]·2MeCN·H2O (M = Fe, 3; Co, 4). 1-4 contain the stacked columns {[M(CN)6]3-;[HAT(CN)6]}∞separated by the organic cations. All of the M-C[triple bond, length as m-dash]N vectors point collectively towards the centroids of pyrazine rings on neighboring HAT(CN)6molecules, with Ncyanidecentroidpyrazinedistances that are under 3 Å. The directional character and structural parameters of the new supramolecular synthons correspond to collective triple anion-π interactions between the CN-ligands of the metal complexes and the π-deficient areas of HAT(CN)6. Physicochemical characterisation (IR spectroscopy, UV-Vis spectroscopy, cyclic voltammetry) and dispersion-corrected DFT studies reveal the dominating charge-transfer (CT) and polarisation characters of the interactions. The electronic density flow occurs from the CN-ligands of [M(CN)6]3-to the HAT(CN)6orbital systems and further, toward the peripheral -CN groups of HAT(CN)6. Solid-state DFT calculations determined the total interaction energy of HAT(CN)6to be ca. -125 kcal mol-1, which gives ca. -15 kcal mol-1per one CN-HAT(CN)6contact after subtraction of the interaction with organic cations. The UV-Vis electronic absorption measurements prove that the intermolecular interactions persist in solution and suggest a 1 : 1 composition of the anion-π {[M(CN)6]3-;[HAT(CN)6]} chromophore, with the formation constant Kadd= (5.8 ± 6) × 102dm3mol-1and the molar absorption coefficient εadd= 180 ± 9 cm-1dm3mol-1at 600 nm, as estimated from concentration-dependent studies.
authors.affiliation: Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland. robert.podgajny@uj.edu.pl.
authors.forename: Jedrzej
authors.initials: J
authors.lastname: Kobylarczyk
authors.affiliation: Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland. robert.podgajny@uj.edu.pl.
authors.forename: Dawid
authors.initials: D
authors.lastname: Pinkowicz
authors.affiliation: Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland. robert.podgajny@uj.edu.pl.
authors.forename: Monika
authors.initials: M
authors.lastname: Srebro-Hooper
authors.affiliation: Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland. robert.podgajny@uj.edu.pl.
authors.forename: James
authors.initials: J
authors.lastname: Hooper
authors.affiliation: Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland. robert.podgajny@uj.edu.pl.
authors.forename: Robert
authors.identifier: http://orcid.org/0000-0001-7457-6799
authors.initials: R
authors.lastname: Podgajny