gadolinium(III) Chloride

Properties

About gadolinium(III) Chloride

Gadolinium(III) chloride is the workhorse soluble Gd(III) source in the lab — anhydrous GdCl3 (263.61 g/mol) is a hygroscopic white powder, but in practice almost everyone buys and uses the hexahydrate GdCl3·6H2O because the anhydrous form is hard to keep dry and harder still to make from the hydrate. Calcining the hydrate in air just gives the basic oxychloride GdOCl with loss of HCl — the classic rare-earth-chemistry trap. Clean dehydration requires either vacuum sublimation, the NH4Cl-assisted route (heat the hydrate with excess NH4Cl under argon, then sublime the NH3·HCl off above 300 °C), or direct synthesis from the metal in a chlorine stream. In the solid the Gd(III) center is nine-coordinate in a tricapped trigonal prismatic geometry — the typical large-Ln(III) coordination number, the same one you see in LaCl3 and CeCl3, all isostructural in the UCl3-type lattice. The medical relevance is enormous: GdCl3·6H2O is the starting material for every Gd-based MRI contrast agent on the market. Magnevist (Gd-DTPA), Dotarem (Gd-DOTA), Gadavist, ProHance, and Eovist are all made by mixing aqueous GdCl3 with the appropriate macrocyclic or open-chain polyaminocarboxylate, adjusting pH, and purifying the chelate — about 30 million doses per year worldwide. GdCl3 is also a stretch-activated ion-channel blocker at micromolar concentrations, used in neurophysiology to dissect mechanotransduction.

Where you'll encounter it

If you have ever weighed out a Gd standard for ICP-MS calibration, you have used GdCl3·6H2O — it dissolves in dilute HNO3 cleanly enough to give a 1000 ppm stock that holds for months. In a cardiac-electrophysiology lab, 30 µM GdCl3 in the bath is the standard tool for blocking Piezo1 stretch-activated channels in cardiomyocytes, with the caveat that Gd3+ also blocks L-type calcium channels at higher doses, so the dose-response curve has to be done carefully. In a contrast-agent manufacturing plant producing Magnevist or Dotarem, GdCl3 solution is mixed with the appropriate polyaminocarboxylate ligand at controlled pH and the chelate is purified by ultrafiltration before vialing — about 30 million doses per year flow through this pipeline globally. In a Czochralski crystal-growth furnace pulling a Gd:YAG laser rod, GdCl3 dopant is co-melted with Y2O3 and Al2O3 at 1970 °C and pulled at a few mm/hour to give a fault-free 6-inch boule.

Common Uses

• Starting material for Gd-DTPA, Gd-DOTA, and other macrocyclic MRI contrast agents
• Mechanosensitive-channel blocker (Piezo1, TRP) at 10-30 µM in patch-clamp experiments
• ICP-MS and ICP-OES calibration standard for trace gadolinium analysis
• Lewis-acid catalyst for Mukaiyama aldol and Friedel-Crafts acylation reactions
• Dopant precursor in Gd:YAG and Gd:YGG laser-crystal Czochralski growth
• Reduction precursor to Gd metal via electrolysis in molten LiCl-KCl eutectic
• Phosphor synthesis dopant in Gd2O2S:Tb x-ray intensifier screens
• Lanthanide-shift NMR reagent precursor for chiral organic substrate analysis

Constituent Elements