Nickel(ii) and iron(ii) triple helicates assembled from expanded quaterpyridines incorporating flexible linkages

Abstract

In the present study the interaction of Fe(II) and Ni(II) with the related expanded quaterpyridines, 1,2-, 1,3-and 1,4-bis-(5¢-methyl-[2,2¢]bipyridinyl-5-ylmethoxy)benzene ligands (4-6 respectively), incorporating flexible, bis-aryl/methylene ether linkages in the bridges between the dipyridyl domains, was shown to predominantly result in the assembly of [M 2 L 3 ] 4+ complexes; although with 4 and 6 there was also evidence for the (minor) formation of the corresponding [M 4 L 6 ] 8+ species. Overall, this result contrasts with the behaviour of the essentially rigid 'parent' quaterpyridine 1 for which only tetrahedral [M 4 L 6 ] 8+ cage species were observed when reacted with various Fe(II) salts. It also contrasts with that observed for 2 and 3 incorporating essentially rigid substituted phenylene and biphenylene bridges between the dipyridyl domains where reaction with Fe(II) and Ni(II) yielded both [M 2 L 3 ] 4+ and [M 4 L 6 ] 8+ complex types, but in this case it was the latter species that was assigned as the thermodynamically favoured product type. The X-ray structures of the triple helicate complexes [

A Springloaded Metal-Ligand Mesocate Allows Access to Trapped Intermediates of Self-Assembly

“…The mesocate Fe 2 X 3 ·Py 6 ·(ClO 4 ) 4 (Figure ), formed by heating 2,7-diaminoxanthone ( X ), 2-formylpyridine (PyCHO), and Fe­(ClO 4 ) 2 in acetonitrile, is an interesting example of a strained assembly. In contrast with the many other Fe 2 L 3 helicates known in the literature, Fe 2 X 3 ·Py 6 is paramagnetic at room temperature and displays a red coloration indicative of a weaker ligand field than most Fe-iminopyridine complexes, which are generally diamagnetic and deep purple in color. Displacement experiments illustrate the low stability, as complete displacement of diaminoxanthone from Fe 2 X 3 ·Py 6 is possible upon transimination with diamines such as diamino-suberone under equilibrium conditions (70 °C, <4 h) .…”

Iron(III) Metallacryptand and Metallacryptate Assemblies Derived from Aroylbis(N,N-diethylthioureas)

“…Metallacryptands ( 1 ) and metallacryptates ( 2 ) belong to one of the most well-known classes of compounds, helicates, which have been extensively studied in metallo-supramolecular chemistry. − In addition to the topological analogy between the well-known cryptands and metallacryptands, these compounds have a number of advantages over their organic counterparts. Particularly, they are accessible in high yields in one-pot reactions and exhibit spectroscopic, electronic, and magnetic properties, which are inaccessible with their organic analogues. , Some strategies, namely, Raymond’s symmetry-interaction method and Saalfrank and Albrecht’s template-directed approach, − have been developed and widely used for rational syntheses of aesthetic metallacryptands/metallacryptates.…”

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [FeII2] Supramolecular Helicates

“…[18][19][20][21][22] Some of the reported examples showe vidence that the spin-active centers can be brought from the LS to am etastable HS state in response to light irradiation by the LIESST (light-induced exciteds pin-statet rapping)e ffect. [23] With am ore sophisticated design of ligands, metallohelicates are also amenable to selectively capture guest species inside them, [24][25][26][27] which offers av aluable opportunity for modulating the functional properties of their components,s uch as the switchingb ehavior of potential SCO metals. In fact, such at uning of the SCO behaviort hrough encapsulation of guests is extremelyr are in supramolecular chemistry,a nd when encountered, it has indeed led to only very minor effects.…”