Alkoxy- and thiolato-bridged Re(I) molecular rectangles [{(CO)3Re(mu-ER)2Re(CO)3}2(mu-bpy)2] (ER = SC4H9, 1a; SC8H17, 1b; OC4H9, 2a; OC12H25, 2b; bpy = 4,4'-bipyridine) exhibit strong interactions with several planar aromatic molecules. The nature of their binding was studied by spectral techniques and verified by X-ray diffraction analysis. Standard absorption and fluorescence titrations showed that a relatively strong 1:1 interaction occurs between aromatic guests such as pyrene and these rectangles. The results of a single-crystal X-ray diffraction analysis show that the recognition of 1 with a pyrene molecule is mainly due to CH...pi interactions and the face of the guest pyrene is located over the edges of the bpy linkers of 1. This is a fairly novel example of an interaction that is rarely designed into a host-guest pair. Furthermore, the interaction of 1 with Ag+ results in the self-organization of supramolecular arrays, as revealed by solid-state data.
A novel one‐pot synthesis of rhenium‐based triangular prismatic cages has been accomplished in excellent yields by a self‐assembly strategy. Reaction of Re2(CO)10 with 2,4,6‐tri‐4‐pyridyl‐1,3,5‐triazine (tpt) in the presence of an aliphatic alcohol (1‐butanol, 1‐octanol or 1‐dodecanol) afforded molecular prisms, [{(CO)3Re(μ2‐OR)2Re(CO)3}3(μ3‐tpt)2] (1, R = C4H9; 2, R = C8H17; 3, R = C12H25) by solvothermal methods. Fine tuning of the solubility is achieved by tailoring the length of the alkyl chain of the alcohol. Compounds 1−3 reported here are the first Re‐containing molecular prisms of the M6L2L′6 type. In addition, they are the first neutral, prismatic cages without counterions that are highly air and moisture stable. Compounds 2 and 3 are soluble in most common organic solvents and they exhibit a large solvatochromism: the value of λmaxab could be tuned over 125 nm simply by changing the polarity of the solvent.
Oxamidato-bridged Re(I)-based supramolecular
rectangles with an
ester functionality have been synthesized via an orthogonal bonding
approach under solvothermal conditions. Self-assembly of Re2(CO)10 and oxamide ligands (H2L1 = N,N′-dibutyloxamide, H2L2 = N,N′-dioctyloxamide,
H2L3 = N,N′-didodecyloxamide,
and H2L4 = N,N′-dibenzyloxamide)
with the pyridyl ligand phenyl-1,4-bis(isonicotinate) (pbin) has resulted
in the formation of metallarectangles of general formula [{(CO)3Re(μ-η4-L)Re(CO)3}2(μ-pbin)2] (1–4), wherein L = N,N′-dibutyloxamidato
(1), N,N′-dioctyloxamidato
(2), N,N′-didodecyloxamidato
(3), N,N′-dibenzyloxamidato
(4) and pbin = phenyl-1,4-bis(isonicotinate). The metallarectangles
have been characterized using spectroscopic techniques, and single-crystal
X-ray structures have been obtained for 1 and 4. The guest binding ability of 2 has been investigated
with a few aromatic amines and an amino ketone using electronic absorption
and fluorescence emission spectroscopy, and the results revealed a
strong binding interaction between host–guest species. The
luminescence properties of 2 and 3 have
been tuned using organic–aqueous solvent mixtures.
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