Neutral ditopic flexible N-donor ligands (Ln = bis(4-(naphtho[2,3-d]imidazol-1-ylmethyl)phenyl)methane, L1 bis(4-(benzimidazol-1-ylmethyl)phenyl)methane, L2 or bis(4-(2-nonylbenzimidazol-1-ylmethyl)phenyl)methane, L3) possessing a bis(4-methylphenyl)methane spacer with two imidazolyl donor units were designed and synthesized. The ligands were utilized to develop metallacavitands analogous to irregular pentagonal-shaped metallacavitands with larger cavities. The metallacavitands 1-4 were assembled from Re2(CO)10, a rigid bis-chelating donor (1,4-dihydroxy-9,10-anthraquinone or chloranilic acid) and Lnvia a solvothermal approach. The ligands and the metallacavitands were characterized by analytical and spectroscopic methods. The molecular structures of 1 and 4 were further confirmed by single crystal X-ray diffraction analysis which revealed that a toluene molecule resides in the hydrophobic cavity. Ln and 1-4 are emissive in DMSO at room temperature. The internal cavity of the metallacavitand acts as a host for aromatic guest molecules. The host-guest interaction properties of 1 with anthracene, naphthalene, nitrobenzene, 2-nitrotoluene, 4-nitrotoluene and 2,4-dinitrotoluene were studied by an emission spectroscopic method.
Calix[4]arene-analogous technetium
supramolecules (1 and 2) were assembled
using (NBu4)[Tc2(μ-Cl)3(CO)6] and neutral flexible
bidentate nitrogen-donor ligands (L1 and L2)
consisting of four arene units covalently joined via methylene units.
The neutral homoleptic technetium macrocycles adopt a partial cone/cone-shaped
conformation in the solid state. These supramolecules are the first
example of fac-[Tc(CO)3]+ core-based
metallocalix[4]arenes and second example of fac-[Tc(CO)3]+ core-based metallomacrocycles. Structurally
similar fac-[Re(CO)3]+ core-based
macrocycles (3 and 4) were also prepared
using [Re(CO)5X] (where X = Cl or Br) and L1 or L2. The products were characterized spectroscopically
and by X-ray analysis.
The design and self‐assembly of supramolecular coordination complexes (SCCs) i. e., discrete cyclic metalloarchitectures such as cycles, cages, mesocates, and helicates with desired size, shape, and properties have been increasing exponentially owing to their potential applications in molecular sensors, molecular cargos, molecular recognition, and catalysis. The introduction of the organic motifs and metal complexes as a spacer provides functionality to the metalloarchitecture. This review mainly focusses on newly evolving spacer based ligands employed to yield simple to high‐order metallosupramolecular assemblies using straight‐forward approaches. The new spacers including corannulene, organic cyclic framework, bicyclic organic motifs, aliphatic chain, metalloligands, triarylboron, BODIPY, azaphosphatrane, phosphine, and thio/selenophosphates offer a great set of properties and in‐built functionalities to the metalloarchitectures which are discussed in this review.
The self-assembly of three rheniumtricarbonyl core-based
supramolecular
coordination complexes (SCCs), fac-[Re(CO)3(μ-L)(μ-L′)Re(CO)3] (1–3) was carried out using Re2(CO)10, rigid bis-chelating ligand (HO∩N-Ph-N∩OH
(L1) (where HO∩N = 2-hydroxyphenylbenzimidazolyl),
and flexible ditopic N-donor ligands (L2 = bis(3-((1H-benzoimidazol-1-yl)methyl)-2,4,6-trimethylphenyl)methane,
L3 = bis(3-((1H-naphtho[2,3-d]imidazol-1-yl)methyl)-2,4,6-trimethylphenyl)methane, L4 = bis(4-(naphtho[2,3-d]imidazol-1-yl-methyl)phenyl)methane) via a one-pot solvothermal approach. In the solid state,
the dinuclear SCCs adopt heteroleptic double-stranded helicate and
meso-helicate architectures. The supramolecular structures of the
complexes are retained in the solution based on the 1H
NMR and electrospray ionization (ESI)-mass analysis. The spectral
and photophysical properties of the complexes were studied both experimentally
and using time-dependent density functional theory (TDDFT) calculations.
All of the supramolecules exhibited emission in both solution and
solid states. Theoretical studies were conducted to determine the
chemical reactivity parameters, molecular electrostatic potential
surface plots, natural population, and Hirshfeld analysis for complexes 1–3. Additionally, molecular docking studies
were carried out for complexes 1–3 with B-DNA.
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