A new 3-D Cd(II) coordination polymer with metallacalix[4]arene building blocks based on 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylic acid

Rhenium(I)-Based Heteroleptic Pentagonal Toroid-Shaped Metallocavitands: Self-Assembly and Molecular Recognition Studies

A family of neutral, heteroleptic, dinuclear M₂LL'-type pentagonal toroid-shaped metallomacrocycles (1-8) were synthesized using flexible ditopic N donors (Lⁿ = L¹-L²), rigid bis-chelating ligands (H₂-L' = H₂-E), and Re₂(CO)₁₀ in a one-pot solvothermal self-assembly approach. The ligands and the metallomacrocycles were characterized using ATR-IR, electrospray ionization mass spectrometry, nuclear magnetic resonance, ultraviolet-visible, and emission spectroscopy methods. The molecular structures of 1, 2, 4, 6, and 7 were confirmed by an X-ray diffraction study and are similar to those of calix[5]arene. The cyclic inner cavities of the metallomacrocycles accommodate toluene/mesitylene/acetone/chlorobenzene as guest molecules that are stabilized by cumulative C-H···π and π···π interactions with the cyclic framework of metallomacrocycle. The photophysical properties of the ligands and the metallomacrocycles were studied. The host-guest recognition properties of metallocavitands 1, 2, 7, and 8 as a model host with phenol and nitrobenzene derivatives as guest molecules were studied by emission spectroscopy methods.

A new one-dimensional CdII coordination polymer incorporating 2,2'-(1,2-phenylene)bis(1H-imidazole-4,5-dicarboxylate)

Imidazole-4,5-dicarboxylic acid (H₃IDC) and its derivatives are widely used in the preparation of new coordination polymers owing to their versatile bridging coordination modes and potential hydrogen-bonding donors and acceptors. A new one-dimensional coordination polymer, namely catena-poly[[diaquacadmium(II)]-μ₃-2,2'-(1,2-phenylene)bis(1H-imidazole-4,5-dicarboxylato)], [Cd(C₁₆H₆N₄O₈)_0.5(H₂O)₂]_n or [Cd(H₂Phbidc)_1/2(H₂O)₂]_n, has been synthesized by the reaction of Cd(OAc)₂·2H₂O (OAc is acetate) with 2,2'-(1,2-phenylene)bis(1H-imidazole-4,5-dicarboxylic acid) (H₆Phbidc) under solvothermal conditions. In the polymer, one type of Cd ion (Cd1) is six-coordinated by two N atoms and two O atoms from one H₂Phbidc^4- ligand and by two O atoms from two water molecules, forming a significantly distorted octahedral CdN₂O₄ coordination geometry. In contrast, the other type of Cd ion (Cd2) is six-coordinated by two N atoms and two O atoms from two symmetry-related H₂Phbidc^4- ligands and by two O atoms from two symmetry-related water molecules, leading to a more regular octahedral coordination geometry. The Cd1 and Cd2 ions are linked by H₂Phbidc^4- ligands into a one-dimensional chain which runs parallel to the b axis. In the crystal, the one-dimensional chains are connected through hydrogen bonds, generating a two-dimensional layered structure parallel to the ab plane. Adjacent layers are further linked by hydrogen bonds, forming a three-dimensional structure in the solid state.

A new two-dimensional managnese(II) coordination polymer constructed by 2,2'-(1,2-phenylene)bis(1H-imidazole-4,5-dicarboxylate)

In recent years, N-heterocyclic carboxylate ligands have attracted much interest in the preparation of new coordination polymers since they contain N-atom donors, as well as O-atom donors, and have a rich variety of coordination modes which can lead to polymers with intriguing structures and interesting properties. A new two-dimensional coordination polymer, namely poly[[μ₃-2,2'-(1,2-phenylene)bis(4-carboxy-1H-imidazole-5-carboxylato)-κ⁶O⁴,N³,N^3',O^4':O⁵:O^5']manganese(II)], [Mn(C₁₆H₈N₄O₈)]_n or [Mn(H₄Phbidc)]_n, has been synthesized by the reaction of Mn(OAc)₂·4H₂O (OAc is acetate) with 2,2'-(1,2-phenylene)bis(1H-imidazole-4,5-dicarboxylic acid) (H₆Phbidc) under solvothermal conditions. In the polymer, each Mn^II ion is six-coordinated by two N atoms from one H₄Phbidc^2- ligand and by four O atoms from three H₄Phbidc^2- ligands, forming a significantly distorted octahedral MnN₂O₄ coordination geometry. The Mn^II ions are linked by hexadentate H₄Phbidc^2- ligands, leading to a two-dimensional structure parallel to the ac plane. In the crystal, adjacent layers are further connected by N-H...O hydrogen bonds, forming a three-dimensional structure in the solid state.

Rhenium(i) based irregular pentagonal-shaped metallacavitands

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.