Color-tunable upconversion-emission switch based on cocrystal-to-cocrystal transformation

The charge transfer cocrystal of any one of the preceding claims, wherein the charge transfer cocrystal is color-tunable by substituting the electron donor for a second, different electron donor.

The charge transfer cocrystal of any one of the preceding claims, wherein the macrocycle is a triangular macrocycle.

The charge transfer cocrystal of any one of the preceding claims, wherein the electron donor is a substituted anthracene or a substituted naphthalene.

The charge transfer cocrystal of any one of the preceding claims, wherein the electron donor is an anthracene substituted with one or more halogen or a naphthalene substituted with one or more halogen.

The charge transfer cocrystal of any one of the preceding claims, wherein the electron donor is an anthracene substituted with one or more Cl or a naphthalene substituted with one or more Cl.

The charge transfer cocrystal of any one of the preceding claims, wherein the electron donor is 9, 10-dichloroanthracene (DCA) or 1-chloronaphthalene (CN).

The charge transfer cocrystal of any one of the preceding claims, wherein the cocrystal is DCA·NDI-Δ or CN·NDI-Δ.

A method for upconverting photons, the method comprising irradiating a charge transfer cocrystal with photons at a first energy state, the charge transfer cocrystal comprising an electron acceptor macrocycle and an electron donor, whereby photons at a second energy state are emitted, the second energy state being higher than the first energy state.