A ternary memory module using low-voltage control over optical properties of metal-polypyridyl monolayers

Kumar, Ajay; Chhatwal, Megha; Mondal, Prakash Chandra; Singh, Vikram; Singh, Alok Kumar; Cristaldi, Domenico A.; Gupta, Rinkoo Devi; Gulino, Antonino

doi:10.1039/c4cc00388h

Cited by 40 publications

(25 citation statements)

References 25 publications

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“…+0.6, +1.1, and +1.6 V vs Ag/AgCl (Scheme 6). 40 The oxidation potentials of the metal centers are separated by 400 mV (Figure 12a), which allows the tuning of the optical properties of the film under selective bias. For a bias within the +(0.6−1.1) V range, Os 2+ oxidation occurred, with concomitant hypochromic shift of the most-intense 1 MLCT band at λ max = 503 nm and disappearance of the weaker 3 MLCT band at λ max = 687 nm (Figure 12b).…”

Section: Hetero-dinuclear Terpyridyl Complexes As Ternary Memory Modulesmentioning

confidence: 99%

Nanometric Assembly of Functional Terpyridyl Complexes on Transparent and Conductive Oxide Substrates: Structure, Properties, and Applications

2017

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Over the last few decades, molecular assemblies on solid substrates have become increasingly popular, challenging the traditional systems and materials in terms of better control over molecular structure and function at the nanoscale. A variety of such assemblies with high complexity and adjustable properties was generated on the basis of organic, inorganic, organometallic, polymeric, and biomolecular building blocks. Particular versatile elements in this context are terpyridyls due to their wide design flexibility, ease of functionalization, and ability to coordinate to a broad variety of transition-metal ions without forming diastereoisomers, which facilitates tuning of their optical and electronic properties. Specifically, metal-terpyridyl complexes are worthy building blocks for generating optoelectronically active assemblies on technologically relevant transparent and conductive oxide substrates. In this context, the present Account summarizes our recent results on the preparation, characterization, and applications of nanometric (2-10 nm) surface-confined molecular assemblies of Cu, Fe, Ru, and Os-terpyridyl complexes on SiO-based substrates (glass, quartz, silicon, and ITO-coated glass). These assemblies rely on covalent bond formation between the iodo-/chloro-terminated functionalized SiO substrates and the pendant group (mostly pyridyl) hosted on the terpyridyl complexes. Such an anchoring provides excellent thermal, temporal, radiative, and electrochemical stability to the assemblies as needed for technological applications. The functional, covalently assembled monolayers were extended to fabricate molecular dyads (bilayers), triads (trilayers), and oligomers by an established layer-by-layer procedure using suitable metallolinkers such as Cu, Ag, and Pd. The chemical, optical, and electrochemical properties of these assemblies could be precisely adjusted by selection of proper metal-terpyridyl complexes and/or metallolinkers, so that the resulting systems served, relying on the specific design, as sensors, catalysts, molecular logic gates, and photochromic devices. For instance, a Cu-terpyridyl-based assembly on a glass substrate showed "turn on" detection of ascorbic acid. In another example, heterometallic molecular triads were exposed to redox-active NO for selective oxidation of the metal ions, and the optical readout was utilized for configuring multiple-input-based molecular logic gates. Furthermore, bias-driven (+0.6 to +1.6 V vs Ag/AgCl) optical properties of the heteroleptic Ru/Os-terpyridyl monolayers were modulated and "read out" by spectro-electrochemical techniques demonstrating high charge/information density (3-4 × 10 electrons/cm). Moreover, the manipulation of the M (M = Fe, Ru, and Os) redox wave in the assembly provided the possibility to create mixed-valence redox-states paving the way toward the fabrication of "multi-bit" memory systems. We truly believe that due to these intriguing characteristics and excellent stability, terpyridyl-based molecular assemblies have the potential to ...

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Section: Hetero-dinuclear Terpyridyl Complexes As Ternary Memory Modulesmentioning

confidence: 99%

Nanometric Assembly of Functional Terpyridyl Complexes on Transparent and Conductive Oxide Substrates: Structure, Properties, and Applications

2017

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“…12 (Polypyridine)ruthenium(II) complexes, especially the archetype compound [Ru(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine), have found wide application in such arrays due to their high stability and outstanding photochemical properties. Further applications of this class of compounds comprise photosensitizers in dye-sensitized solar cells 13 and emitters in light-emitting electrochemical cells.…”

Section: ■ Introductionmentioning

confidence: 99%

Dual Emission and Excited-State Mixed-Valence in a Quasi-Symmetric Dinuclear Ru–Ru Complex

et al. 2014

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The synthesis and characterization of the new dinuclear dipeptide [(EtOOC-tpy)Ru(tpy-NHCO-tpy)Ru(tpy-NHCOCH3)](4+) 3(4+) of the bis(terpyridine)ruthenium amino acid [(HOOC-tpy)Ru(tpy-NH2)](2+) 1(2+) are described, and the properties of the dipeptide are compared to those of the mononuclear complex [(EtOOC-tpy)Ru(tpy-NHCOCH3)](2+) 4(2+) carrying the same functional groups. 3(4+) is designed to serve a high electronic similarity of the two ruthenium sites despite the intrinsic asymmetry arising from the amide bridge. This is confirmed via UV-vis absorption and NMR spectroscopy as well as cyclic voltammetry. 4(2+) and 3(4+) are emissive at room temperature, as expected. Moreover, 3(4+) exhibits dual emission from two different triplet states with different energies and lifetimes at room temperature. This is ascribed to the presence of a unique thermal equilibrium between coexisting [Ru(II)(tpy-NHCO-tpy(·-))Ru(III)] and [Ru(III)(tpy-NHCO-tpy(·-))Ru(II)] states leading to an unprecedented excited-state Ru(II)Ru(III) mixed-valent system via the radical anion bridge tpy-NHCO-tpy(·-). The mixed-valent cation 3(5+), on the other hand, shows no measurable interaction of the Ru(II)Ru(III) centers via the neutral bridge tpy-NHCO-tpy (Robin-Day class I). Reduction of 3(4+) to the radical cation 3(3+) by decamethylcobaltocene is bridge-centered as evidenced by rapid-freeze electron paramagnetic resonance spectroscopy. Interestingly, all attempts to observe 3(3+) via NMR and UV-vis absorption spectroscopy only led to the detection of the diamagnetic complex 3-H(3+) in which the bridging amide is deprotonated. Hence 3-H(3+) (and 4-H(+)) appear to reduce protons to dihydrogen. The ease of single and double deprotonation of 4(2+) and 3(4+) to 4-H(+), 3-H(3+), and 3-2H(2+) was demonstrated using a strong base and was studied using NMR and UV-vis absorption spectroscopies. The equilibrating excited triplet states of 3(4+) are reductively quenched by N,N-dimethylaniline assisted by hydrogen bonding to the bridging amide.

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“…[21] Molecular memory devices represent an emerging research area in the field of molecular electronics andi nformation technology. [22][23][24] Many attempts to realize memory devices on the molecular scale by applying av ariety of basic memory mechanisms have been reported. The distincte nergyl evels in redoxactive metal complexes can permitastepwise charging through controlled redox reactions,w hich may enablet he storageo fi nformation as volatile and nonvolatile memory by applying voltage.…”

Section: Introductionmentioning

confidence: 99%

Photoresponsive Molecular Memory Films Composed of Sequentially Assembled Heterolayers Containing Ruthenium Complexes

Nagashima

Ozawa

Suzuki

et al. 2015

Chemistry A European J

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Photoresponsive molecular memory films were fabricated by a layer-by-layer (LbL) assembling of two dinuclear Ru complexes with tetrapodal phosphonate anchors, containing either 2,3,5,6-tetra(2-pyridyl)pyrazine or 1,2,4,5-tetra(2-pyridyl)benzene as a bridging ligand (Ru-NP and Ru-CP, respectively), using zirconium phosphonate to link the layers. Various types of multilayer homo- and heterostructures were constructed. In the multilayer heterofilms such as ITO||(Ru-NP)m |(Ru-CP)n , the difference in redox potentials between Ru-NP and Ru-CP layers was approximately 0.7 V, which induced a potential gradient determined by the sequence of the layers. In the ITO||(Ru-NP)m |(Ru-CP)n multilayer heterofilms, the direct electron transfer (ET) from the outer Ru-CP layers to the ITO were observed to be blocked for m>2, and charge trapping in the outer Ru-CP layers became evident from the appearance of an intervalence charge transfer (IVCT) band at 1140 nm from the formation of the mixed-valent state of Ru-CP units, resulting from the reductive ET mediation of the inner Ru-NP layers. Therefore, the charging/discharging ("1"and "0") states in the outer Ru-CP layers could be addressed and interconverted by applying potential pulses between -0.5 and +0.7 V. The two states could be read out by the direction of the photocurrent (anodic or cathodic). The molecular heterolayer films thus represent a typical example of a photoresponsive memory device; that is, the writing process may be achieved by the applied potential (-0.5 or +0.7 V), while the readout process is achieved by measuring the direction of the photocurrent (anodic or cathodic). Sequence-sensitive multilayer heterofilms, using redox-active complexes as building blocks, thus demonstrate great potential for the design of molecular functional devices.

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A ternary memory module using low-voltage control over optical properties of metal-polypyridyl monolayers

Cited by 40 publications

References 25 publications

Nanometric Assembly of Functional Terpyridyl Complexes on Transparent and Conductive Oxide Substrates: Structure, Properties, and Applications

Nanometric Assembly of Functional Terpyridyl Complexes on Transparent and Conductive Oxide Substrates: Structure, Properties, and Applications

Dual Emission and Excited-State Mixed-Valence in a Quasi-Symmetric Dinuclear Ru–Ru Complex

Photoresponsive Molecular Memory Films Composed of Sequentially Assembled Heterolayers Containing Ruthenium Complexes

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