Related Experiment Video
Updated: Sep 9, 2025

Characterization of Synthetic Polymers via Matrix Assisted Laser Desorption Ionization Time of Flight MALDI-TOF Mass Spectrometry
Published on: June 10, 2018
Homoleptic magnesium and calcium complexes supported by constrained reduced Schiff base ligand for lactide
Timothy Quek1, Thonthun Saeteaw1, Tanyawan Pongpanit1
1Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), 555 Moo 1, Payupnai, Wangchan, Rayong 21210, Thailand. khamphee.p@vistec.ac.th.
Abstract:
A homoleptic calcium complex supported by a constrained reduced Schiff base ligand was synthesised and found to be highly active for the ring-opening polymerisation (ROP) of 100 equiv. lactide within 2 min at room temperature. However, the magnesium analogue has significantly lower reactivity. Single-crystal X-ray diffraction revealed a 6-coordinate metal environment for both complexes. Density functional theory (DFT) calculations showed that the calcium complex can asccommodate up to 7-coordination, thereby facilitating polymerisation without detachment of the dimethylamino sidearm, unlike in the magnesium complex. The participation of the phenoxy group and secondary amine (N-H) were observed to facilitate polymerisation via hydrogen bonding.
More Related Videos
Related Concept Videos
Complexometric Titration: Ligands
Ladder Diagrams: Complexation Equilibria
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
EDTA: Chemistry and Properties
Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
Complexation Equilibria: The Chelate Effect
Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...

