The field of self-assembled monolayers (SAMs) has witnessed tremendous growth in synthetic sophistication and depth of characterization over the past 15 years.1 However, it is interesting to comment on the modest beginning and on important milestones. The field really began much earlier than is now recognized. In 1946 Zisman published the preparation of a monomolecular layer by adsorption (self-assembly) of a surfactant onto a clean metal surface.2 At that time, the potential of self-assembly was not recognized, and this publication initiated only a limited level of interest. Early work initiated in Kuhn’s laboratory at Gottingen, applying many years of experience in using chlorosilane derivative to hydrophobize glass, was followed by the more recent discovery, when Nuzzo and Allara showed that SAMs of alkanethiolates on gold can be prepared by adsorption of di-n-alkyl disulfides from dilute solutions.3 Getting away from the moisture-sensitive alkyl trichlorosilanes, as well as working with crystalline gold surfaces, were two important reasons for the success of these SAMs. Many self-assembly systems have since been investigated, but monolayers of alkanethiolates on gold are probably the most studied SAMs to date. The formation of monolayers by self-assembly of surfactant molecules at surfaces is one example of the general phenomena of self-assembly. In nature, self-assembly results in supermolecular hierarchical organizations of interlocking components that provides very complex systems.4 SAMs offer unique opportunities to increase fundamental understanding of self-organization, structure-property relationships, and interfacial phenomena. The ability to tailor both head and tail groups of the constituent molecules makes SAMs excellent systems for a more fundamental understanding of phenomena affected by competing intermolecular, molecular-substrates and molecule-solvent interactions like ordering and growth, wetting, adhesion, lubrication, and corrosion. That SAMs are well-defined and accessible makes them good model systems for studies of physical chemistry and statistical physics in two dimensions, and the crossover to three dimensions. SAMs provide the needed design flexibility, both at the individual molecular and at the material levels, and offer a vehicle for investigation of specific interactions at interfaces, and of the effect of increasing molecular complexity on the structure and stability of two-dimensional assemblies. These studies may eventually produce the design capabilities needed for assemblies of three-dimensional structures.5 However, this will require studies of more complex systems and the combination of what has been learned from SAMs with macromolecular science. The exponential growth in SAM research is a demonstration of the changes chemistry as a disciAbraham Ulman was born in Haifa, Israel, in 1946. He studied chemistry in the Bar-Ilan University in Ramat-Gan, Israel, and received his B.Sc. in 1969. He received his M.Sc. in phosphorus chemistry from Bar-Ilan University in 1971. After a brief period in industry, he moved to the Weizmann Institute in Rehovot, Israel, and received his Ph.D. in 1978 for work on heterosubstituted porphyrins. He then spent two years at Northwestern University in Evanston, IL, where his main interest was onedimensional organic conductors. In 1985 he joined the Corporate Research Laboratories of Eastman Kodak Company, in Rochester, NY, where his research interests were molecular design of materials for nonlinear optics and self-assembled monolayers. In 1994 he moved to Polytechnic University where he is the Alstadt-Lord-Mark Professor of Chemistry. His interests encompass self-assembled monolayers, surface engineering, polymers at interface, and surfaces phenomena. 1533 Chem. Rev. 1996, 96, 1533−1554

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Formation and Structure of Self-Assembled Monolayers.

Signaling Recognition Events with Fluorescent Sensors and Switches.

Ru(II) polypyridine complexes: photophysics, photochemistry, eletrochemistry, and chemiluminescence

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation {(C2H5)3NH}[Ru(H3tcterpy)(NCS)3] 1, {(C4H9)4N}2[Ru(H2tcterpy)(NCS)3] 2, {(C4H9)4N}3[Ru(Htcterpy)(NCS)3] 3, and {(C4H9)4N}4[Ru(tcterpy)(NCS)3] 4 (tcterpy = 4,4‘,4‘ ‘-tricarboxy-2,2‘:6‘,2‘ ‘-terpyridine) have been synthesized and fully characterized by UV−vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a RuIIN6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better π-acceptor properti...

Engineering of Efficient Panchromatic Sensitizers for Nanocrystalline TiO2-Based Solar Cells

It was suggested that in a series of osmium (II) polypyridyl compounds the properties of their metal-to-ligand charge-transfer (MLCT; Os/sup II/ --> pi* (bpy) or (phen)) excited states including luminescence lifetimes, emission maxima, and redox potentials were systematically variable by making chemical changes The authors have prepared a more extensive series of compounds and with the extended series are able to identify systematic variations in both nonradiative (k/sub nr/) and radiative rate constants (k/sup r/), and the systematic variations have important implications for transition-metal photochemistry They give some relevant excited-state parameters for a series of mono- and bis-2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) complexes of Os(II)

Application of the energy gap law to the decay of charge-transfer excited states

The syntheses of complexes derived from the planar, tridentate ligand 2,2',2''-terpyridine (trpy) of the type (trpy)Ru/sup II/(L)Cl/sub 2/ where L = PPh/sub 3/, P(p-C/sub 6/H/sub 4/Me)/sub 3/, or pyridine are described. Some rather striking differences in the properties of the cis and trans-isomers of the phosphine derivatives are reported. (BLM).

Cis-trans isomerism in (trpy)(PPh3)RuC12. Comparisons between the chemical and physical properties of a cis-trans isomeric pair

The cyclic voltammetry of fac-Re(bpy)(CO)3Cl (bpy = 2,2′-bipyridine) and of the intermediate complexes formed by bulk electrolysis in MeCN solution in the presence and absence of CO2 has been interpreted in terms of two different electrocatalytic pathways for the reduction of CO2 to Co, one involving an initial one-electron reduction and the other an initial two-electron reduction.

One- and two-electron pathways in the electrocatalytic reduction of CO2 by fac-Re(bpy)(CO)3Cl (bpy = 2,2′-bipyridine)

Hydrogen-bonding-induced solvatochromism in the charge-transfer transitions of ruthenium(II) and ruthenium(III) ammine complexes

Preparation des complexes cis-[M(bpy) 2 (TFMS) 2 ] + ou M est le rhodium ou l'iridium, bpy est la bipyridine, TFMS est le trifluoromethanesulfonate. Etude de l'activite catalytique de ces complexes au cours de la reduction du CO 2 par voie electrochimique

B. Patrick Sullivan

Papers

Application of the energy gap law to the decay of charge-transfer excited states

Cis-trans isomerism in (trpy)(PPh3)RuC12. Comparisons between the chemical and physical properties of a cis-trans isomeric pair

One- and two-electron pathways in the electrocatalytic reduction of CO2 by fac-Re(bpy)(CO)3Cl (bpy = 2,2′-bipyridine)

Hydrogen-bonding-induced solvatochromism in the charge-transfer transitions of ruthenium(II) and ruthenium(III) ammine complexes

Electrocatalytic reduction of carbon dioxide by 2,2'-bipyridine complexes of rhodium and iridium