# US 11,993,615 B2 · Altering thermochromic transition temperature in transition metal ethylenediamine complexes by substitutional doping of anionic species

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- Number: US 11,993,615 B2
- Document ID: US11993615B2
- Status: Granted
- Kind: B2
- Application number: 17/961,585
- Filed: 2022-10-07
- Published: 2024-04-11
- Granted: 2024-05-28
- Earliest claimed: 2022-10-07
- Assignees: The Government of the United States of America, as represented by the Secretary of the Navy
- Applicants: The Government of the United States of America, as represented by the Secretary of the Navy
- Inventors: James August Ridenour
- Web page: https://patentgrep.com/patent/US11993615B2

## CPC

- C07F 15/045: {without a metal-carbon linkage}
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)

## Abstract

Tunable thermochromic materials comprise a metal salt with a varying proportion of two different anions and an organic ligand. Partial substitution via doping during the initial synthesis with a macro-structurally similar (generating an isostructural material) yet chemically different anion creates a material with altered thermochromic properties. For example, in bromide-doped bis(N,N′-diethylethylenediamine)nickel(II)) tetrafluoroborate; both the tetrafluoroborate (BF4-) and bromide (Br—) derivatives are isostructural. Substitution of BF4- for Br— causes a decrease in the materials' thermochromic transition temperature by approximately 10° C.

## Claims

### Claim 1

A tunable thermochromic material comprising:
a first instance of an organic ligand complexed with a metal salt; and two different anions present in a first proportion; and
a second instance of the organic ligand complexed with the metal salt and the two different anions, wherein the two different anions are present in a second proportion differing from the first proportion,
wherein, as a consequence of the different proportions, the first instance has a different thermochromic transition temperature from that of the second instance,
wherein the thermochromic transition is reversible with a change in temperature, and
wherein the organic ligand is an N,N′-disubstituted diamine.

### Claim 2 (depends on 1)

The material of claim 1, wherein the anions are selected from the group consisting of BF4−, ClO4−, NO3−, Br−, and I−.

### Claim 3

A tunable thermochromic material comprising:
a first instance of N,N′-diethylethylenediamine operating as a ligand and complexed with a metal salt; and two different anions present in a first proportion, wherein the anions are tetrafluoroborate (BF4−) and bromide (Br−); and
a second instance of N,N′-diethylethylenediamine operating as a ligand complexed with the metal salt and the two different anions, wherein the two different anions are present in a second proportion differing from the first proportion,
wherein, as a consequence of the different proportions, the first instance has a different thermochromic transition temperature from that of the second instance, and
wherein the thermochromic transition is reversible with a change in temperature.

### Claim 4 (depends on 3)

The material of claim 3, wherein the metal salt comprises nickel.

### Claim 5

A method of preparing a tunable thermochromic material, the method comprising:
providing in a first solvent two different anions present in a first proportion and a metal salt;
adding an organic ligand to the solvent, thereby causing a first thermochromic material to precipitate;
providing in a second solvent the two different anions present in a second proportion and the metal salt;
adding the organic ligand to the second solvent, thereby causing a second thermochromic material to precipitate,
wherein the first and second thermochromic materials differ only in the proportions of the two different anions,
wherein the ligand is an N,N′-disubstituted diamine, and
wherein, as a consequence of the different proportions, the first material has a different thermochromic transition temperature from that of the second material, and
wherein the thermochromic transition is reversible with a change in temperature.

### Claim 6 (depends on 5)

The method of claim 5, wherein the anions are selected from the group consisting of BF4−, ClO4−, NO3−, Br−, and I−.

### Claim 7 (depends on 5)

The method of claim 5, wherein the ligand is N,N′-diethylethylenediamine.

### Claim 8 (depends on 5)

The method of claim 5, wherein:
the anions are tetrafluoroborate (BF4−) and bromide (Br−);
the metal salt comprises nickel; and
the ligand is N,N′-diethylethylenediamine.