The name/synonym for ligand PG4 (curated from ChEBI, PubChem, and PDB databases):

1TETRAETHYLENE GLYCOL
23,6,9-TRIOXAUNDECANE-1,11-DIOL
33,6,9-TRIOXAUNDECAN-1,11-DIOL
4PEG-4
52,2'-[OXYBIS(2,1-ETHANEDIYLOXY)]BISETHANOL
62,2'-[OXYBIS(ETHANE-2,1-DIYLOXY)]DIETHANOL
72-(2-[2-(2-HYDROXYETHOXY)ETHOXY]ETHOXY)ETHANOL
8POLYETHYLENE GLYCOL PEG400