[16] a) Assuming a hexagonal arrangement of the porous structures of the micro-and meso-porous silica matrices, FSM-16, as indicated in the XRD and TEM results, Equation 1 can be derived from a geometrical consideration,where W 0 is the pore volume per unit weight, a is the lattice constant from the XRD result, t is the thickness of the pore wall, and r is the density of the pore wall, which is assumed to be 2.2 g mL
±1.The thickness of the pore wall, t, can be obtained as a constant value of 0.9 nm from the plot of W 0 as a function of a. The pore diameter, d, can be estimated as a±t. b) M. Hruk, M. Jaroniec, A. Sayari, J. Phys. Chem. B, 1997, 101, 583. [17] S. Inagaki, A. Koiwai, N. Suzuki, Y. Fukushima, K. Kuroda, Bull. Chem. Soc. Jpn. 1996, 69, 1449 A Multi-Addressable Photochromic 1,2-Dithienylcyclopentene-Phenoxynaphthacenequinone Hybrid** By Andrew J. Myles, Tony J. Wigglesworth, and Neil R. Branda*The current interest in miniaturizing the components of machinery and electronics down to the molecular level is a major impetus to developing molecular systems that display switchable properties.[1] Photochromic compounds exhibit reversible variations in their physical characteristics when stimulated by light [1,2] and are some of the best contenders for use in electro-optical devices and memory media, where each isomer of the photochromic compound can represent ª0º or ª1º of a digital code. [3] One key aspect in the progress of molecular switching technology is the development of more complex systems that integrate several switchable functions into a single molecule. Memory media capable of processing more than two pieces of information at the same storage site is an illustrative example of an application of the use of multi-addressable switching strategies. Several impressive examples of multi-addressable switching systems have been reported with as many as six addressable states existing within the same molecule.[4] However, their practical application is limited due to the thermal reversibility of the switching units in almost all cases, the inability to access all states in most cases, and the fact that addition of chemical reagents is often required. A thermally stable, multi-addressable, all-photon mode system is more desirable as it will benefit from the fast response times and the ease at which monochromatic light can be tuned and focused when it is used as the switching stimulus. Few of the photochromic compounds known today display the favorable properties of 1,2-dithienylcyclopentene derivatives (DTE). These compounds undergo the thermally irreversible photochemical cyclization reactions (DTE-o > DTE-c) illustrated in Scheme 1, with a high degree of fatigue resistance, making them the most promising candidates for molecular read/write systems.[5] Scheme 1 also presents the photochromic phenoxynaphthacenequinone (PNQ) motif, which interconverts between its trans-(PNQ-t) and ana-forms (PNQ-a), also with a high level of thermal irreversibility and fatigue resistance. [6] We present here an all-pho...