Molecular Keypad Lock Research Articles

DNA-based logic gates operating as a biomolecular security device

The first example of a nucleic acid-based molecular keypad lock has been constructed by taking advantage of the sequence-specific recognition ability of DNA and solid-phase substrates.

Azobenzene-based system for fluorimetric sensing of H2PO4− (Pi) that works as a molecular keypad lock

A 'novel' and cost-effective 'on-off'-type monophosphate H(2)PO(4)(-) (Pi) chemosensor based on the mononuclear 2,2'-dihydroxyazobenzene (DHAB)-Zn(ii) complex was developed and a molecular keypad lock can be realized in the DHAB-based system by using Zn(ii) cations and Pi anions as inputs.

Digital Operations with Molecules - Advances, Challenges, and Perspectives

This Review gives a short introduction into molecular logic and focusses then on the latest advances in the field. With regard to complex logic circuits and functions, molecular devices for arithmetic processing (adders and subtractors), multiplexers/demultiplexers, and encoders/decoders are discussed. Further on, the concept of memory for data storage and sequential logic is considered together with the latest results on molecular keypad locks. Molecular logic has been often connected to the future aim of molecular computing. However, albeit the herein described approaches constitute a starting point, major challenges like concatenation of gates, solid state devices and compartmentalization, and alternative concepts (reversible logic, multivalued logic) are waiting ahead. These points are included, as well as a view on alternative applications of molecular logic in bio-inspired approaches, combinatorial chemistry, and materials science.

A Double Plug–Socket System Capable of Molecular Keypad Locks through Controllable Photooxidation

Two robust divalent complexes have been successfully constructed by using complementary rigid spacers (anthracene vs. 1,4,5,8-naphthalenediimide (NDI)) and two pairs of [24]crown-8 ethers and secondary dialkylammonium functionalities as binding motifs. It was demonstrated that properly selected, rigid spacers are more efficient than flexible ones for achieving strong multivalent association. This is presumably due to the preorganization of the rigid spacers, the cooperation between charge-transfer interactions of rigid spacers, and the complexation of the binding motifs. Furthermore, the intermolecular photoinduced electron transfer (PET) between rigid spacers in these robust complexes could be switched on and off by modulating their complexation through acid-base reactions, which is reminiscent of a plug-socket system capable of electron transfer. In addition, the self-sensitized photooxidation of the divalent host with anthracene as a spacer can be completely inhibited after complexation with the divalent guests that contain NDI as spacers. This process could also be understood by invoking intermolecular PET and could be turned on and off through acid-base reactions. The photophysical and photochemical properties of these robust complexes have been interpreted as molecular keypad locks with alarm systems. Thus, a double plug-socket system and molecular keypad locks were successfully integrated inside robust multivalent systems and then the normal molecular devices were endowed with logic functions.

An All‐Photonic Molecular Keypad Lock

Off and on: A molecular triad, consisting of a porphyrin linked to two different, independently addressable photochromic moieties, functions as a molecular keypad lock with all-photonic inputs and output. The porphyrin correlates the responses of the two inputs to light of different wavelengths and provides an appropriate output as fluorescence, which results only when one of eight possible input combinations has been applied (see figure).

Logic circuits constructed with an ion-sensitive fluorescent molecule 1,2-di[5-methoxy-2-(2-pyridyl)thiazoyl]ethyne

The fluorescence behaviours of a chemical-sensitive fluorescent molecule 1,2-di[5-methoxy-2-(2-pyridiyl)thiazoyl]ethyne (DMPTE) at different protonation and coordination states were studied. Upon addition of protons, metal ions and other chemicals, the fluorescent states can be switched reversibly. On the basis of the changes of fluorescence output signals from particular wavelengths in response to different combination sets of two particular external stimuli, the entire set of 2-bit Boolean binary logic functions were realized at the molecular level, including PASS 0, PASS 1, YES, NOT, OR, NOR, INHIBIT, IMPLICATION, AND, NAND, XOR, XNOR, and different logic functions were integrated reconfigurably within DMPTE. Besides, starting from the same initial state, a series of three-input logic gates and circuits were also constructed. Furthermore, the stepwise recognition process of DMPTE to different chemical input signals can also be utilized to distinguish different input sequences, thus a molecular keypad lock that authenticates three-digit password entries is indicated.

Superimposed molecular keypad lock and half-subtractor implications in a single fluorophore

The ionic inputs to new fluorophore have been mimicked as a superimposed electronic molecular keypad lock and half-subtractor.

A reversible fluorescent Hg2+/K+ switch that works as keypad lock in the presence of F− ion

A thiacalix[4]arene based fluorescent chemosensor 3 of 1,3-alternate conformation bearing two dansyl groups and a crown-5 ring behaves as an "On-Off" reversible switch for two chemical inputs Hg(2+) and K(+) ions and mimics a molecular level keypad lock in the presence of F(-) ions.

A simple chemosensor for Hg2+ and Cu2+ that works as a molecular keypad lock

A new chemosensor which can detect Hg(2+) in water and Hg(2+)/Cu(2+) in acetonitrile and its application as a molecular keypad lock using Cu(2+) and F(-) as ionic inputs are demonstrated.