Ligand exchange thermochromic systems containing exchange metals
Ligand exchange of thermochromic, LETC, systems exhibiting a reversible change in absorbance of electromagnetic radiation as the temperature of the system is reversibly changed are described. The described LETC systems include one or more than one transition metal ion, which experiences thermally induced changes in the nature of the complexation or coordination around the transition metal ion(s) and, thereby, the system changes its ability to absorb electromagnetic radiation as the temperature changes. In accordance with one aspect of the present invention, a thermochromic system is disclosed comprising a first metal ion and a second metal ion and at least one ligand that complexes with the first metal ion to form a LεMLC and complexes with the second metal ion to form a HεMLC wherein an increase in temperature of the system results in a reversible net increase in its ability to absorb light energy in the 400 nm to 1400 nm range due to the ligand transferring from the first metal ion to the second metal ion.
1. A thermochromic system comprising a first metal ion and a second metal ion and at least one ligand that complexes with a first metal ion to form a LεMLC and that complexes with a second metal ion to form a HεMLC, wherein the thermochromic system exhibits a reversible net increase in its ability to absorb light energy in the visible and/or NIR range as the temperature of the system is increased as a result of the ligand transferring from the first metal ion to the second metal ion.
2. The thermochromic system of claim 1 wherein the system exhibits a reversible net increase in its ability to absorb light energy in the visible range.
3. The thermochromic system of claim 2 wherein the first metal ion is Zn(II) and the second metal ion is a combination of Co(II) and Ni(II).
4. The thermochromic system of claim 2 wherein the ligand is a phosphine oxide, a phosphinate or an imidazole.
5. The thermochromic system of claim 2 wherein the ligand is chloride, bromide, iodide or thiocyanate.
6. The thermochromic system of claim 1 wherein the system exhibits a reversible net increase in its ability to absorb light energy in the NIR range.
7. The thermochromic system of claim 1 wherein the first metal ion is Zn(II) or Mn(II), and the second metal ion is selected from Co(II), Ni(II) or Cu(II).
8. The thermochromic system of claim 7 wherein the first metal ion is Ni(II) and the second metal ion is Cu(II).
9. The thermochromic system of claim 7 wherein the first metal ion is Zn(II) and the second metal ion is Cu(II) or Co(II).
10. The thermochromic system of claim 9 wherein the ligand includes a halide or pseudohalide.