A supramolecular keypad lock

Abstract

The reversible photoswitching between an anthracene derivative and its [4+4] dimer, using the template effect of the CB8 macrocycle, was demonstrated. This example of supramolecular chemistry in water was harnessed to demonstrate the operation of a keypad lock device that is driven by means of light and chemicals as inputs.The use of molecular species for achieving information processing of chemical, photonic or electrochemical signals according to the principles of binary coding (0 and 1) and Boolean language continues to receive wide attention. [1][2][3] The challenge of achieving the design of molecules that are capable of a predetermined logic operation has received important backup from smart applications of molecular logic gates in sensing, drug delivery, theranostics, and materials chemistry. [4][5][6][7][8][9][10] Among the different logic operations, those that imply a memory function belong to the most demanding ones in terms of their chemical design. 11 This type of logic, known as sequential logic, results in differentiated outputs depending on the input history of the device. Current research activities along these lines have their focus on the implementation of flip-flops and molecular keypad locks. Photochromic switches have been often exploited for these purposes. [12][13][14][15] However, chemically-addressable systems and redox-switchable molecular devices were also used for the demonstration of molecular keypad locks [16][17][18][19] and flip-flops. 20,21 Surprisingly, the exploitation of supramolecular host-guest phenomena for the demonstration of keypad lock functions has no precedence in the literature. In recent reports host-guest complexes with cucurbit [7]uril (CB7) and cucurbit [8]uril (CB8) were used to demonstrate the reconfigurable and resettable operation of logic gates in aqueous solution. 22,23 Cucurbiturils have drawn much attention for their very high binding constants of cationic guests (up to 10 17 M À1 ) 24 and their supramolecular application potential with a strong focus on biological and pharmacological contexts, and analytical problems is beginning to reveal. [25][26][27][28][29][30][31][32][33][34][35] In the present work we take advantage of the specific complexation properties of the CB8 macrocycle. Unlike the smaller homologues CB6 and CB7, that commonly offer space for only one guest molecule, the larger CB8 often accommodates two guests and the resulting complexes may feature new emission properties (e.g., excimer fluorescence) or lead to fluorescence self-quenching. [35][36][37][38] Additionally, the resulting pre-organization of the two guests may facilitate intracomplex photoreactions that would not happen at the dilute concentrations of the free dye molecules. [38][39][40] In a wider context, host-templated photodimerizations have been used in the design of photoswitchable supramolecular polymers. [40][41][42] Herein we designed the anthracene derivative 1 (see the ESI † for details of the synthesis and Scheme 1 for the structure) which contains a positively ...

Message in a molecule

“…Figure 4 shows a means for complicating such efforts by entering a password as an additional layer of defence. This approach exploits the principles of molecular keypad lock technology303132333435363738394041, which largely rely on the tendency of multivalent host–guest complexes and multicomponent assemblies to be entrapped in local minima41. We selected ZnCl 2 ( 1 ), Na 3 PO 4 ( 2 ) and NaOH ( 3 ) as representative entry keys owing to the strong interaction of Zn(II) with DPA ligands5556, as well as with NaOH or Na 3 PO 4 to yield Zn(OH) 2 and zinc phosphate complexes, respectively62.…”

“…Unlike its predecessor414243, however, or any other fluorescent probe that responds to several analytes2444 or an analyte group43, m-SMS was designed to operate as a universal sensor that can discriminate among a vast number of distinct chemical species. We show that this property not only distinguishes m-SMS from other types of fluorescent molecular sensors, but also from other chemical security systems45678910111213141516171819202122272829303132333435363738394041 by enabling it to function as a molecular cipher device that can convert distinct chemical structures into unique encryption keys. In this way, the system can be used not only to hide the data (steganography), but also to encrypt and decrypt it (cryptography), as well as provide password protection when a higher level of security is needed.…”

“…Another important advantage of using molecular steganography systems, namely, their small scale, has also been demonstrated by the ability to conceal messages within individual DNA strands21. Finally, advances in the area of molecular logic gates2223242526 have resulted in alternative methods of securing information222728 by using multi-analyte fluorescent molecular sensors that can produce ID-codes29 or can authorize password entries303132333435363738394041.…”

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

“…At the same time, this effect of the ligand–CB[ n ] interplay may be used to modify and control the photochemical properties of a guest molecule [8–9]. For instance, the encapsulation of photoactive molecules in the constrained medium of a cucurbituril cavity enables the performance of chemo-, regio- or stereoselective photoreactions that are not possible in homogeneous solution [10–15]. …”

Terpenes Show Nanomolar Affinity and Selective Binding with Cucurbit[8]uril

“…[5,6] Hence it is not a surprise that organic molecules with protonable or peralkylated heteroatoms are preferred. In general high binding constants result, which are an additional asset for the widely recognized application potential of cucurbiturils in sensing and switching, [8][9][10][11][12][13][14][15] biomolecule modification, [4,[16][17][18][19] and delivery, [14,[20][21][22][23][24][25] to name just a few examples. [7] In some cases the complexation is also entropically favored.…”