Contractile and Extensible Molecular Figures‐of‐Eight

Abstract

Two large rings, 66- (m-66) and 78-membered (m-78) rings, each one incorporating two pairs of transition-metal-complexing units, have been prepared. The coordinating fragments are alternating bi- and tridentate chelating groups, namely, 2,9-diphenyl-1,10-phenanthroline (dpp) and 2,2',2',6''-terpyridine (terpy) respectively. Both macrocycles form molecular figures-of-eight in the presence of Fe(II) , affording a classical bis-terpy complex as the central core. The larger m-78 ring can accommodate a four-coordinate Cu(I) center with the formation of a {Cu(dpp)2 }(+) central complex and a highly twisted figure-of-eight backbone, whereas m-66 is too small to coordinate Cu(I) . Macrocycle m-78 thus affords stable complexes with both Fe(II) and Cu(I) ; the ligand around the metal changes from (terpy)2 to (dpp)2 . This bimodal coordination situation allows for a large amplitude rearrangement of the organic backbone. When coordinated to preferentially octahedrally coordinated Fe(II) or Cu(II) , the height of the molecule along the coordinating axis of the tridentate terpy ligands is only about 11 Å, whereas the height of the molecule along the same vertical axis is several times as large for the tetrahedral Cu(I) complex. Chemically or electrochemically driven contraction and extension motions along a defined axis make this figure-of-eight particularly promising as a new class of molecular machine prototype for use as a constitutive element in muscle-like dynamic systems.

Chiral macrocyclic terpyridine complexes

“…Attempts to maintain chirality in terpyridine complexes range from the attachment of chiral groups 9 – 11 to their integration into macrocyclic structures. 12 , 13 Two terpyridines facing each other in the periphery of macrocycles complemented by additional coordination sites result in chiral metal complexes. The most prominent examples are the macrocycle complemented by two additional ethylenediamine units reported by Bazzicalupi et al which forms a dimetallic helical structure upon coordination of two Cu( ii ) ions 12 and the huge macrocycles complemented by two additional phenanthrolines reported by Niess et al which form chiral figure-of-8 shaped Fe( ii ) complexes.…”

“…The most prominent examples are the macrocycle complemented by two additional ethylenediamine units reported by Bazzicalupi et al which forms a dimetallic helical structure upon coordination of two Cu( ii ) ions 12 and the huge macrocycles complemented by two additional phenanthrolines reported by Niess et al which form chiral figure-of-8 shaped Fe( ii ) complexes. 13 While these figure-of-8 complexes are examples of chiral terpyridine complexes, they were only reported as racemic mixtures. Terpyridine complexes have also been used as linkers closing the periphery of macrocycles.…”

Strong and Selective Halide Anion Binding by Neutral Halogen‐Bonding [2]Rotaxanes in Wet Organic Solvents

“…Mechanically interlocked molecules (MIM) such as rotaxanes and catenanes have progressed from compounds of aesthetic interesta nd curiosity to an active area of contemporary chemical research, with applications in nanotechnology, [1][2][3][4][5][6][7][8] drug delivery, [9][10][11][12] catalysis, [13][14][15] materials science [16][17][18][19][20][21] and molecular recognition. [22][23][24][25] Amongst the supramolecular interactions, which imbue interlocked host systemswith their unique recognition properties for anion guest species, halogen bonding (XB), the highly directional attractive non-covalent interaction between an electron-deficient halogen atom and aL ewis base, [26,27] remains the least exploited.…”

Successive Translocation of the Rings in a [3]Rotaxane

“…The powder was dissolved in CH 2 Cl 2 (20 mL) and washed with 1 m HCl (3 10mL), H 2 O( 310 mL), and brine (3 10 mL). The organic layer was dried over MgSO 4 [2]- (1,7,14,6,15,5,9,12,16,18,22,tetrabenzocyclohexacosane)-[N,N'-bis(12-{[4-(2,2-diphenylethylamino)-4oxobutanoyl]amino}dodecyl)-pyromellitic diimide]-rotaxane (2) and [3]-Bis (1,7,14,20-tetraaza-2,6,15,19-tetraoxo-3,5,9,12,16,18,22,25- Solutions of isophthaloyl dichloride (271 mg, 1.34 mmol) in chloroform (10 mL) and p-xylylenediamine (182 mg, 1.34 mmol) with triethylamine (375 mL, 2.67 mmol) in chloroform (10 mL) were simultaneously added by using motor-driven syringe pumps over 4h to as olution of thread 1 (190 mg, 0.167 mmol) in chloroform (25 mL). Following the addition, the mixture was stirred for 16 hb efore removal of the off-white precipitate by filtration.…”

“…[9][10][11] Others are better viewed as information processors, [12] or function as single-molecular chemical factories. [13,14] For the design of molecular muscles different approaches have been explored, [15][16][17][18] but the use of mechanically interlocked building blocks is advantageous because it allows to put constraints on the relative movements of the components. [19][20][21][22][23][24][25][26][27] In the present work, we describe the translation of either one or both of the macrocyclic rings in a [3]rotaxane by one-electron or two-electron reduction of a central diimide.…”