Molecular AND and INHIBIT Gates Based on Control of Porphyrin Fluorescence by Photochromes

Abstract

A molecular triad consisting of a porphyrin (P) covalently linked to two photochromes-one from the dihydroindolizine family (DHI) and one from the dihydropyrene family (DHP)-has been synthesized and found to act as either a molecular AND logic gate or an INHIBIT gate, depending on the inputs and initial state of the photochromes. The basis of these functions is quenching of porphyrin fluorescence (output of the gates) by the photochromes. The spiro form of DHI does not quench porphyrin fluorescence, whereas its betaine isomer strongly quenches by photoinduced electron transfer. DHP also quenches porphyrin fluorescence, but its cyclophanediene isomer does not. The triad has been designed using suitable energetics and electronic interactions, so that although these quenching phenomena may be observed, independent isomerization of the attached photochromes still occurs. This makes it possible to switch porphyrin fluorescence on or off by isomerization of the photochromes using various combinations of inputs such as UV light, red light, and heat.

Control of Noise in Chemical and Biochemical Information Processing

“…Indeed, chemical processes can be cast [35,36] in the language of computing operations, with signals represented by changes [1][2][3][4][36][37][38][39][40][41][42][43][44][45][46][47][48] in structural, chemical, or physical properties, resulting due to physical, chemical, [77][78][79][80][81][82][83][84] or more than one type [53,[85][86][87] of input. The output signals can be detected spectroscopically [88][89][90][91][92][93] or electrically/electrochemically. [94][95][96] Chemical computing can be done in the bulk, e.g., in solution, [97][98] or at surfaces/interfaces, [14-17,99-102[ such as at electrodes or on Si-chips.…”

Tetranucleotides as a scaffold for diporphyrin arrays

“…Major interests in these constructs are in the imitation of the antenna complex of the natural photosynthetic system [2], in enzyme mimics [3,4], and in the design and synthesis of new molecular electronic [5] and photonic [6] devices. The strategies employed to build the porphyrin arrays use either direct covalent connection [7][8][9][10][11], a metal-to-ligand complexation approach [12][13][14][15], or noncovalent hydrogen-bonding patterns [16][17][18][19].…”

Molecular 2:1 Digital Multiplexer

“…[17] The CPD and DHI chromophores have no significant effect on the photophysics of the porphyrin excited singlet state, and normal porphyrin fluorescence from CPD-P-DHI is observed (Figure 3). The lifetime of the porphyrin first excited singlet state is 11 ns, which is essentially identical to that of model porphyrins.…”

“…[17] The triad consists of a tetraarylporphyrin (P) linked to both a substituted dihydropyrene photochrome and a photochrome of the dihydroindolizine family based on pyrrolo [1,2-b]pyridazine. Because each photochrome may exist in two metastable forms, the triad may assume any of four isomeric structures (Figure 1).…”

“…Although the three chromophores of 1 interact photochemically (vide infra), photoisomerization of the two photochromes still occurs, and it is possible to prepare photostationary distributions greatly enriched in each of the four isomers. [17] For the multiplexer, only three isomers are required: CPD-P-DHI, DHP-P-DHI, and CPD-P-BT. Isomer CPD-P-DHI features the dihydropyrene in the colorless cyclophanediene (CPD) form and the dihydroindolizine in the colorless spiro form (DHI).…”