Controlling the isomerization rate of Azo-BF2 switches using aggregation

A method of controlling the isomerization rate of a compound, comprising:

• (a) selecting a compound capable of isomerizing between a thermally stable isomer and a kinetic isomer, and wherein thermal relaxation is concentration-dependent;
• (b) providing a solution of the compound having a preset concentration of the compound;
• (c) exposing the solution to electromagnetic radiation having a wavelength effective to cause isomerization of the compound in the solution to the kinetic isomer;
• and
• (d) shielding the solution from electromagnetic radiation to allow for thermal relaxation of the kinetic isomer, thereby controlling the isomerization rate of the compound, wherein the preset concentration is determined by:
• (e) measuring the number of molecules of the compound per unit volume (concentration) that provides a desired half-life of the kinetic isomer, step (e) preceding step (b);
• wherein the compound is of Formula II:
• or a salt thereof, wherein
• N═N—R2 can be oriented cis or trans to the tricycle;
• R1 is H, CN, CO2H, CO2(C1-6-alkyl), C1-6-alkyl, C6-19-aryl, OH, O(C1-6-alkyl), OC(O)(C1-6-alkyl), NH2, NH(C1-6-alkyl), N(C1-6-alkyl)2, or NHC(O)(C1-6-alkyl);
• R2 is phenyl;
• and
• R3, R4, R5, R6, Wand R8 are each, independently, H, C1-6-alkyl, C6-19-aryl, OH, O(C1-6-alkyl), OC(O)(C1-6-alkyl), NH2, NH(C1-6-alkyl), N(C1-6-alkyl)2, NHC(O)(C1-6-alkyl) or a group corresponding to a small molecule pharmaceutical;
• or
• R3 and R4, R4 and R5, R5 and R6 or R7 and R8 can, when taken together, form a fused aryl, fused heteroaryl, fused C3-6-cycloalkyl, or fused heterocycle, wherein the fused aryl, fused heteroaryl, fused cycloalkyl, or fused heterocycle can be optionally substituted one or more times with C1-6-alkyl, C6-19-aryl, OH, O(C1-6-alkyl), OC(O)(C1-6-alkyl), NH2, NH(C1-6-alkyl), N(C1-6-alkyl)2, or NHC(O)(C1-6-alkyl), wherein said step (c) takes place in a mammalian cell.