Recent Advances in Molecular Logic Gates

Versatile chemistry of Bodipy dyes allows the design and straightforward synthesis of multivalent-multitopic derivatives, which, with judicious selection of metal ion-ligand pairs based on known affinities, affords control and manipulation of photoinduced electron transfer and internal charge transfer processes as desired. We have demonstrated that metal ions acting as modulators (or inputs, in digital design parlance) can generate absorbance changes in accordance with the operation of a halfadder. In addition, an AND logic gate in the emission mode was delivered using a different binucleating arrangement of ligands. A molecular equivalent of a three-input AND logic gate was also obtained exploiting differential binding affinities of metal ions for different ligands. The results suggest that different metal ions can be used as nonannihilating inputs, selectively targeting various ligands incorporated within a single fluorophore, and with careful design, diverse photophysical processes can be selectively modulated, resulting in a range of signals, useful in molecular logic design, and offering an enticing potential for multianalyte chemosensors. In this work,* we demonstrated that, with prior knowledge of respective binding affinities of metal ions for various ligands, it should be possible to design molecular logic gates using different metal ions as inputs. Bodipy chemistry is particularly useful in this regard, because it allows straightforward placement of ICT and PET donors on the same molecule, which increases signal diversity to a great extent. Styryl modifications of Bodipy proved to be a useful reaction. In the three examples presented, this modification allowed us to place ICT donor functionalities at strategically important positions. The result is straightforward syntheses of the target molecules, with responses compatible with AND logic, and a molecular half-adder with nonannihilating inputs. Outputs compatible with XOR logic have been difficult to attain without the use of self-annihilating (such as acids and bases, either Lewis or Bronsted-Lowry) inputs, but in the half-adder described in this work, this is done by the differential selective interactions between the ligands and the metal ions selected. Using signals obtained by exploiting the relative selectivity of inputs for different ligands/chelators, more challenging molecular logic operations should be within reach.

O. Altan Bozdemir, Ruslan Guliyev, Onur Buyukcakir, Sencer Selcuk, Safacan Kolemen, Gulcihan Gulseren, Tugrul Nalbantoglu, Hande Boyaci and Engin U. Akkaya JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132, 8129-8036 (2010)

*Editorially selected for the cover of June 16 issue of the journal.