Dynamic Aminal-Based TPA Ligands.
The use of dynamic covalent reactions (DCRs) is gaining popularity for the construction of self-assembling architectures. We have recently introduced DCRs that exchange alcohols and aldehydes to create hemiaminal ethers within tri(2-picolyl)amine (TPA) ligands, all of which are templated by Zn(II). To expand the scope of this assembly, aromatic imines derived from pyridine-2-carboxyaldehyde were explored as dynamic covalent receptors for di(2-picolyl)amine in the presence of Zn(II) to create TPA ligands that contain aminal linkages. This represents another metal-templated in situ multicomponent assembly. The stability of the assembly was successfully modulated through substituent effects, and the equilibrium constants from imines to aminals were correlated by a linear free energy relationship (LFER) with σ(+) values. Dynamic component exchange was investigated as a means of probing multiple equilibriums quantitatively in the system. Further, the mechanism was analyzed with a qualitative kinetics study. NMR spectra reveal the different extents of two competing pathways for assembly depending upon whether the aromatic amine has electron-withdrawing or electron-donating groups on the ring. Finally, mass spectral evidence supports the presence and differing extents of dominance of the two pathways as a function of the substituents.
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002 (P.R. China).|College of Chemistry, Fuzhou University, Fuzhou, 350116 (P.R. China).
Yuntao
Y
Zhou
College of Chemistry, Fuzhou University, Fuzhou, 350116 (P.R. China).
Yaofeng
Y
Yuan
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002 (P.R. China). lyou@fjirsm.ac.cn.
Lei
L
You
Department of Chemistry, The University of Texas at Austin, Austin, Texas, 78712 (USA). anslyn@austin.utexas.edu.
Eric V
EV
Anslyn
D000447:Aldehydes / Q000138:chemical synthesis / Q000737:chemistry; D000588:Amines / Q000138:chemical synthesis / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry*; D007097:Imines / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D010848:Picolinic Acids / Q000138:chemical synthesis / Q000737:chemistry*; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry; D015032:Zinc / Q000737:chemistry
C501847:2,2'-dipicolylamine; D000447:Aldehydes; D000588:Amines; D006841:Hydrocarbons, Aromatic; D007097:Imines; D008024:Ligands; D010848:Picolinic Acids; D011725:Pyridines; C523774:pyridine-2-carboxaldehyde; D015032:Zinc
imines; ligands; molecular recognition; self-assembly; substituent effects; zinc