Selenolato-bridged
manganese(I)-based dinuclear metallacycles [{(CO)3Mn(μ-SeC6H5)2Mn(CO)3}(μ-L)]
(1–4) were achieved in a
single-step process by the self-assembly of dimanganese decacarbonyl,
diphenyl diselenide, and flexible ditopic ester-functionalized pyridyl
ligands [1, L = o-phenylene diisonicotinate
(pdi); 2, L = 1,6-hexanediyl di-4-pyridine carboxylate
(hdp); 3, L = 4-pyridine carboxylic acid diethylene glycol
diester (pcadgd); 4, L = 4-pyridine carboxylic acid triethylene
glycol diester (pcatgd)]. Synthesis of a series of selenolato-bridged
dinuclear Mn(I)-based metallacycles was facilitated via oxidative
addition of C6H5Se–SeC6H5 to (CO)5Mn–Mn(CO)5 with simultaneous
coordination of flexible ditopic pyridyl linkers in an orthogonal
fashion. The metallacycles were characterized by IR, UV–vis,
NMR, and electrospray ionization-mass spectroscopic techniques and
elemental analysis. Solid-state structural elucidation of 3 was carried out using single-crystal X-ray diffraction methods.
In addition, anticancer activity studies were carried out for compounds 2–4 with various cancer cell lines. Furthermore, compound 3 was probed to evaluate its potential CO-releasing property
using myoglobin assay.
Supramolecular
one-step self-assembly of dimanganese decacarbonyl,
diaryl diselenide, and linear dipyridyl ligands (L = pyrazine (pz),
4,4′-bipyridine (bpy), and trans-1,2-bis(4-pyridyl)ethylene
(bpe)) has resulted in the formation of selenolato-bridged manganese(I)-based
metallorectangles. The synthesis of tetranuclear Mn(I)-based metallorectangles
[{(CO)3Mn(μ-SeR)2Mn(CO)3}2(μ-L)2] (1–6) was facilitated by the oxidative addition of diaryl diselenide
to dimanganese decacarbonyl with the simultaneous coordination of
linear bidentate pyridyl linker in an orthogonal fashion. Formation
of metallorectangles 1–6 was ascertained
using IR, UV–vis, NMR spectroscopic techniques, and elemental
analyses. The molecular mass of compounds 2, 4, and 6 were determined by ESI-mass spectrometry. Solid-state
structural elucidation of 2, 3, and 6 by single-crystal X-ray diffraction methods revealed a rectangular
framework wherein selenolato-bridges and pyridyl ligands define the
shorter and longer edges, respectively. Also, the guest binding capability
of metallorectangles 3 and 5 with different
aromatic guests was studied using UV–vis absorption and emission
spectrophotometric titration methods that affirmed strong host–guest
binding interactions. The formation of the host–guest complex
between metallorectangle 3 and pyrene has been explicitly
corroborated by the single-crystal X-ray structure of 3•pyrene. Moreover, select metallorectangles 1–4 and 6 were studied to explore
their anticancer activity, while CO-releasing ability of metallorectangle 2 was further appraised using equine heart myoglobin assay.
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