Binding of zinc(II) macrocycles toward carboxylate ligands

Abstract

Three new zinc(II) complexes, Zn(L1)(NO 3 ) 2 (1), {[Zn(L1)(fumarate)]Á2H 2 O} n (2) and {[Zn(L2)(fumarate)]Á DMF} n (3) (L = 3 ,14-dimethyl-2,6,13,17-tetraazatricyclo [14,4,0 1.18 ,0 7.12 ]docosane) have been synthesized and characterized by analytical, spectroscopic, thermal and X-ray diffraction methods. The structure of the discrete neutral complex (1) shows that the central zinc(II) ion is coordinated axially by two nitrate ligands. In the structures (2) and (3), the carboxylate groups of the bridging fumarate ligands are coordinated to zinc(II) macrocycles, resulting in the formation of 1D coordination polymers. Apart from the fairly strong Zn-O bonds in (2) and (3), it is observed that the hydrogen bonds between the pre-organized N-H groups of the macrocycle and axial ligands appear to be important for the design and development of metal complexes having a strong Zn-O bond.

Syntheses, Structural, and Spectroscopic Properties of Copper(II) Complexes of Constrained Macrocyclic Ligands

“…The axial Cu1–O2 (H 2 O) distance of 2.693(3) Å is longer than the corresponding bond lengths in [Cu(cyclam)(H 2 O) 2 ]F 2 · 4H 2 O [2.484(6) Å], [Cu(cyclam)(DMF) 2 ](PF 6 ) 2 [2.3985(17) Å], [Cu(L 1 )(H 2 O) 2 ]Cl 2 [2.649(2) Å], [Zn(L 1 )(H 2 O) 2 ]Cl 2 [2.388(3) Å], [Zn(L 1 )(NO 3 ) 2 ] [2.3123(12) Å], and [Zn(L 1 )(OAc) 2 ] · 0.5H 2 O [2.2940(7) Å] 25–30. The observed chromophore CuN 4 O 2 is very similar to those found in [Cu(L 1 )(NO 3 ) 2 ] · 3H 2 O15 and [Cu(L 1 )(ClO 4 ) 2 ] 16.…”

A New Class of Metal-Cyclam-Based Zirconium Metal–Organic Frameworks for CO2 Adsorption and Chemical Fixation

“…(1) MOF structures with open axial coordination sites must be developed. Thus far, in reported cyclam-based MOFs, the core metal participated in the structural backbone of the framework, consequently precluding guest binding and subsequent metal-mediated reactivity. − (2) The synthetic modification of the parent cyclam molecule to incorporate MOF binding groups (carboxylic acids) must not electronically deactivate the compound. A common strategy is to bind the carboxylic groups to the coordinating amines.…”

“…Such modification allows the cyclam to serve as a linear linker while minimizing the electronic effects on the metal–tetra­amine core. Second, the carboxylic acid substituents utilized are minimally flexible, which restricts the ability for the groups to interact with the metallic core of the same cyclam, as is commonly seen in reported structures. − Inspired by the outstanding chemical and thermal stability of Zr­(IV)-based MOFs, − we use Zr­(IV) in the construction of the metal nodes for the cyclam-based MOFs.…”