Anion-pi recognition between [M(CN)(6)](3-) complexes and HAT(CN)(6): structural matching and electronic charge density modification

作者：Kobylarczyk Jedrzej; Pinkowicz Dawid; Srebro Hooper Monika; Hooper James; Podgajny Robert

来源：Dalton Transactions, 2017, 46(11): 3482-3491.

DOI：10.1039/c7dt00293a

Hexacyanidometalates (M = Fe-III, Co-III) and multisite anion receptor HAT(CN)(6) (1,4,5,8,9,11-hexaazatri-phenylenehexacarbonitrile) 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)]}(infinity) separated by the organic cations. All of the M-Cu equivalent to N vectors point collectively towards the centroids of pyrazine rings on neighboring HAT(CN)(6) molecules, with N-cyanide. ..centroid(pyrazine) distances that are under 3 angstrom. The directional character and structural parameters of the new supramolecular synthons correspond to collective triple anion-p interactions between the CN- ligands of the metal complexes and the p-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)(6) orbital systems and further, toward the peripheral -CN groups of HAT(CN)(6). Solid-state DFT calculations determined the total interaction energy of HAT(CN)(6) to be ca. -125 kcal mol(-1), which gives ca. -15 kcal mol-1 per one CN-...HAT(CN)(6) contact 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-pi {[M(CN)(6)](3-);[HAT(CN)(6)]} chromophore, with the formation constant K-add = (5.8 +/- 6) x 10(2) dm(3) mol(-1) and the molar absorption coefficient epsilon(add) = 180 +/- 9 cm(-1) dm(3) mol(-1) at 600 nm, as estimated from concentration-dependent studies.

• 出版日期2017-3-21