No abstract

We report on the first successful output of electrons directly from photosystem I (PSI) of thermophilic cyanobacteria to the gate of a field-effect transistor (FET) by bypassing electron flow via a newly designed molecular wire, i.e., artificial vitamin K(1), and a gold nanoparticle; in short, this newly manufactured photosensor employs a bio-functional unit as the core of the device. Photo-electrons generated by the irradiation of molecular complexes composed of reconstituted PSI on the gate were found to control the FET. This PSI-bio-photosensor can be used to interpret gradation in images. This PSI-FET system is moreover sufficiently stable for use exceeding a period of 1 year.

The chemical functionalization of hydrogen-terminated silicon(111) surfaces with photochromic diarylethene using an ethylene anchoring group was achieved. Conductive atomic force microscopy measurements showed the current changes on modified silicon electrodes caused by light-induced isomerization of the diarylethene between an open form and a closed form.

The simple combination of square planar coordination geometry of Pd(II) or Pt(II) with pyridine-based ligands offers an efficient method for the self-assembly of nanometer-sized frameworks such as macrocycles, cages, catenanes, tubes, and capsules. 1 To expand the structures of pyridyl-coordinated Pd(II) complexes into more rigid and bigger coordination frameworks, one can replace a mono-coordinating 4-pyridyl group by a doubly ligating 3,5-bis-(3-pyridyl)phenyl unit. According to this idea, 4,4′-bipyridine, which is the simplest pyridine-based bridging ligand, is modified into tetradentate ligand 1). This ligand is expected to take a panellike conformation and, on complexation with (en)Pd(NO 3 ) 2 (2), assemble into large discrete box structures such as 3 12+ and 4 16+ in analogy to the assembly of trinuclear and tetranuclear cyclic complexes from 2 and 4,4′-bipyridine. 2,3 Here we report that these expected box structures are efficiently formed in a dynamic fashion. Namely, the boxes are in equilibrium and smoothly interconvertable. Coldspray ionization mass spectroscopy (CSI-MS), which was developed recently by some of us, 4 is found to be very effective to study both kinetic and thermodynamic products in the assembly process (Scheme 1).Treatment of 2 (1.25 × 10 -2 mmol) with ligand 1 (0.62 × 10 -2 mmol) at 50°C for 4 d in D 2 O-CD 3 OD (1:1, 0.5 mL) gave rise to one major product, which was assigned as tetrameric box 4 16+ by CSI-MS after being isolated as PF 6 salt in 88% yield (prominent peaks at m/z ) 1688.8 [4‚13PF 6 ] 3+ and 1230.8 [4‚ 12PF 6 ] 4+ ). In 1 H NMR, a set of six protons was observed in consistent with the D 4h structure of 4 16+ .In addition to box 4 16+ , uncharacterized minor products were also detected in 1 H NMR. Being in equilibrium, all of the products constituted a dynamic library of box structures from a single ligand. 5 From the library, we found that two box structures, both Sasaki, O.; Mitsuhashi, T.; Fujita, T.; Yazaki, J.; Yamaguchi, K.; Ogura, K. J. Chem. Soc., Chem. Commun. 1996, 1535 Rauter, H.; Mutikainen, I.; Blomberg, M.; Lock, C. J. L.; OmarOchoa, P.; Freisinger, E.; Randaccio, L.; Chiarparin, E.; Lippert, B. .-H.; Morishita, H.; Tanaka, K.; Biradha, K.; Furusho, S.; Shionoya, M. Chem. Commun. 2000, 971. (4) Cold ESI-MS is a sort of electrospray ionization (ESI) MS operated under low temperature: Sakamoto, S.; Fujita, M.; Kim, K.; Yamaguchi, K.Figure 1. (a) X-ray structure of coordination box 6 16+ . (b) The linkage connectivity in 6 16+ involving two conformations (A and B). Scheme 1 980