Using CoCl2 and a chiral tecton possessing C2 chirality and based on two coordination poles composed of a pyridine unit connected at the 4-position to a pyridine bearing at the 2 and 6 positions two ...optically active oxazoline moieties, a polar solid is obtained. The latter results from the acentric packing of directional 1-D coordination networks.
The terpy‐derived (terpy=terpyridine) ligand 1 has an extended W shape in which the two appended photoactive pyrenyl groups are held apart. On binding of a zinc(II) ion with a terpy group, ligand 1 ...is converted into complex 2 whereby it adopts a U shape, thus stacking the aromatic units. This structural modification leads to a very pronounced change in photophysical properties: from a highly fluorescent free ligand to a very weakly emitting complex. The W/U structural switching can be reversibly induced by the addition of a competitive tren ligand, which binds and releases a zinc(II) ion under protonation/deprotonation cycles, thus leading to oscillations in light emission. Therefore, the present system performs periodic modulation of optical output through a nanomechanical shape‐flipping motion, triggered by metal ion binding and fuelled by acid–base neutralisation energy. Overall, it represents an ion‐triggered opto‐mechanical supramolecular device.
Le ligand 1 dérivé de la terpyridine (terpy) présente une forme en extension W dans laquelle les deux groupes photoactifs pyrényles, greffés aux deux extrémités, sont maintenus éloignés. La complexation d'un cation ZnII accompagné d'un groupe terpy conduit à un complexe 2 dans lequel le ligand adopte une forme en U, causant de ce fait un rapprochement des extrémités et un empilement des groupes aromatiques. Ce changement de structure produit une modification très prononcée des propriétés photophysiques allant d'un ligand fortement fluorescent à un complexe qui ne l'est que très faiblement. La commutation W/U peut être induite réversiblement par addition d'un agent complexant compétitif, le ligand tren, qui lie et relibère un ion ZnII au cours de cycles de protonation/déprotonation, produisant de ce fait des oscillations de l'émission de lumière. Le système décrit réalise ainsi une modulation périodique du signal optique par l'effet d'un mouvement nanomécanique de changement de forme, déclenché par la fixation d'un ion métallique et dont l'énergie est fournie par la réaction de neutralisation acide/base. Il représente un dispositif supramoléculaire opto‐mécanique à déclenchement ionique.
Molecular signalisation process: An ion‐triggered opto‐mechanical device is described in which a terpyridine‐derived ligand undergoes reversible switching between the fluorescent W‐shaped state of the free ligand (see scheme left) and the nonfluorescent U‐shaped state of its zinc complex (see scheme right).
NMR, mass spectrometry and X-ray diffraction studies show reversible structural interconversion between helical and extended forms of pyridine derived oligoamide molecular strands, by simple ...protonation/deprotonation.
The combination of the same organic tecton
1
, a
meta
-pyridyl appended tetramercaptotetrathiacalix4arene in 1,3-alternate conformation offering four pyridyl units and eight thioether groups, with ...three silver salts AgX (X = BF
4
−
, NO
3
−
and SbF
6
−
) leads, under identical conditions (concentration, temperature and solvent system), to the formation of different silver coordination networks. Both the connectivity and the dimensionality of the three silver coordination networks depend on the nature of the anion used as a counter ion. Whereas the weakly coordinating BF
4
−
anion does not participate in the formation of the non-tubular 1D coordination network, the coordinating NO
3
−
anion is bound to the metal cation and this leads to the formation of a tubular 1D silver coordination network. In both cases, the eight S atoms of the tecton
1
do not take part in the binding of the cation. In marked contrast, when the SbF
6
−
anion is used as a counter ion, the organic tecton
1
behaves as a tetrakismonodentate through its four
meta
-pyridyl moieties and as a bischelating unit of the SCCS type leading thus to the formation of a porous 3D diamondoid-type network.
Structural and coordination propensity of anions directs the connectivity and dimensionality of
meta
-pyridyl appended tetramercaptotetrathiacalix4arene in 1,3-alternate conformation silver coordination networks.
The isomeric bis(tridentate) hydrazone ligand strands 1 a–c react with Ru(terpy)Cl3 (terpy=2,2′:6′,2′′‐terpyridine) to give dinuclear rack‐type compounds 2 a–c, which were characterised by several ...techniques, including X‐ray crystallography and NMR methods. The absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in rigid matrix at 77 K) of the ligand strands 1 a–c and of the metal complexes 2 a–c have been studied. Compounds 1 a–c exhibit absorption spectra dominated by intense π–π* bands, which, in the case of 1 b and 1 c, extend within the visible region, while the absorption spectra of the rack‐type complexes 2 a–c show intense bands both the in the UV region, due to spin‐allowed ligand‐centred (LC) transitions, and in the visible, due to spin‐allowed metal‐to‐ligand charge‐transfer (MLCT) transitions. The energy position of these bands strongly depends on the ligand strand: in the case of 2 a, the lowest energy MLCT band is around 470 nm, while in 2 b and 2 c, it lies beyond 600 nm. Ligands 1 a–c undergo oxidation processes that involve orbitals based mainly on the CH3NN fragments. The complexes 2 a–c undergo reversible metal‐centred oxidation, while reductions involve the hydrazone‐based ligands: in 2 b and 2 c, the bridging ligand is reduced twice and in 2 a once before reduction of the peripheral terpy ligands takes place. Ligands 1 a–c exhibit luminescence from the lowest‐lying 1π–π* level. Only for complex 2 a does emission occur; this may be attributed to a 3MLCT state involving the bridging ligand. Taken together, the results clearly indicate that the structural variations introduced translate into interesting differences in the spectroscopic, luminescence and redox properties of the ligand strands as well as of the rack‐type metal complexes.
La réaction des ligands bidentates isomères de type bishydrazone 1 a–c avec Ru(terpy)Cl3, conduit aux complexes dinucléaires 2 a–c. Les études radiocristallographiques par diffractionole rayons X montrent que les complexes 2 a,b contenant le noyau pyrimidine 4,6‐disubstitué comme unité centrale présentent une courbure, alors que le complexe 2 c, qui a pour unité centrale la pyrazine 2,5‐disubstituée, est à peu près linéaire. Quand l'unité centrale est dérivée d'un dialdéhyde, les complexes sont verts (2 b,c; absorption à 600 nm), alors que lorsqu'elle est dérivée d'une bishydrazine, le complexe correspondant 2 a est brun‐rouge (absorption à 470 nm). Ce dernier est le seul complexe à présenter une émission, alors que les ligands 1 a–c sont tous luminescents. D'un point de vue électrochimique, les ligands 1 a–c participent à des processus irréversibles d'oxydation. Les complexes 2 a–c subissent des oxydations réversibles ou quasi‐réversibles et présentent plusieurs réductions réversibles dans le domaine de potentiel de −2.00 à +2.00 V/ECS. Ces résultats mettent en lumière les modifications des propriétés structurales et physico‐chimiques produites dans les complexes métalliques par le remplacement d'un noyau pyrimidine (2 a,b) par un noyau pyrazine (2 c) ou par le changement de position de la fonction hydrazone (2 a et 2 b,c). Ils permettent d'envisager la synthèse de complexes de plus grande taille à sites multiples, présentant une courbure/linéarité et des propriétés contrôlables par la nature du ligand.
A series of ruthenium(II) rack‐type dinuclear complexes were prepared, the structural features and spectroscopic properties of which are modulated by the nature of the central heterocyclic ring. When the central unit is pyrimidine‐derived, the shape is curved, but it is globally linear when the central unit is pyrazine‐derived (see picture).
Three
p-H
-thiacalix4arene pyridyl appended coordinating tectons (
24
) in a 1,3-alternate conformation have been prepared and structurally characterised in the solid state. These compounds are ...positional isomers differing only by the position of the nitrogen atom on the pyridyl ring. Their combinations with HgCl
2
lead to the formation of 1- and 2-D neutral mercury coordination networks. Whereas for tecton
2
(
ortho
isomer) a 2D architecture resulting from the bridging of consecutive tectons by the mononuclear HgCl
2
unit is obtained, for tecton
3
(
meta
isomer) again a 2D network is formed. However, in that case, the interconnection of consecutive organic tectons
3
takes place through a binuclear Hg
2
Cl
4
species. Finally, in the case of tecton
4
(
para
position), a 1D ribbon type double chain arrangement resulting from the bridging of consecutive tectons by trinuclear Hg
3
Cl
6
units followed by the interconnection of two chains through the fusion of the trinuclear centres into a hexanuclear node is observed.
Combinations of
p-H
-butylthiacalix4arene pyridyl appended positional isomers
24
in a 1,3-A conformation with HgCl
2
lead to the formation of 1- and 2-D neutral mercury coordination networks.
The combination, under mild conditions, of the methylenecarboxylic-appended tetramercaptotetrathiacalix4arene (TMTCA) derivative
4
, blocked in the 1,3-alternate conformation, with acetate salts of ...octahedral copper(
ii
), manganese(
ii
), nickel(
ii
) and zinc(
ii
) leads to the formation, in the crystalline state, of high dimensional coordination networks. Depending on the nature of the used metal cations and bases (pyridine or non-coordinating Et
3
N), six new different high-dimensional coordination polymers have been evidenced, presenting 4 different coordination patterns. All the compounds present a metal/
4
ratio equal to 2/1. The formation of a 2D grid-like compound (
4
-Zn
2
(Py)
4
) and three different pseudodiamondoid-like 3D compounds (
4
-Co
2
(Py)
6
(H
2
O)
2
,
4
-Ni
2
(Py)
6
(H
2
O)
2
,
4
-Mn
2
(Py)
4
(MeOH)
2
,
4
-Mn
2
(DMF)
2
(MeOH)
4
and
4
-Zn
2
(MeOH)
4
) is observed.
Tetrasubstituted methylenecarboxylic-appended tetra-mercaptotetrathiacalix4arene (TMTCA), combined with transition metals, lead to high-dimensional coordination polymers.
Three new organic tectons (
2-4
) based on the
p-tert
-butylthiacalix4arene backbone, blocked in the 1,3-alternate conformation, bearing four pyridyl coordinating moieties, have been synthesised and ...characterised in the solid state. The ligands are positional isomers and differ by the position of the N atom on the pyridyl unit (
ortho
for
2
,
meta
for
3
and
para
for
4
). Their combination with the Ag
+
cation leads, reproducibly, to the formation of 2- and 3-D infinite silver coordination networks. Independent of the nature of the anion, the combination of
2
offering four (N,S) type chelates with the Ag
+
cation affords an unprecedented diamond type 3D network. Both
3
and
4
, behaving as tetrakis monodentate ligands, lead to the formation of 2-D architectures.
Three new organic tectons (
2-4
) based on the
p-tert
-butylthiacalix4arene backbone, blocked in the 1,3-alternate conformation, bearing four pyridyl coordinating moieties, have been synthesised and characterised in the solid state.
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