The electronic spectrum of [Pt(tpy)Cl]+ (tpy = 2,2':6',2"-terpyridine) is influenced dramatically by intermolecular stacking interactions in solution and in the solid state. The crystal structure of [Pt(tpy)Cl]ClC>4 (monoclinic, P2\!c (No. 14); a = 7.085(2), b = 17.064(5), c = 26.905(8) Á; ß = 90.0(1)°; Z = 8) consists of discrete Pt2 units (Pt-Pt = 3.269(1) Á) arranged along an infinite tpy-stack (spacing ~3.35 Á). Variable-temperature and concentration studies of the absorption and emission spectra of [Pt(tpy)Cl]+ suggest that similar metal-metal and ligand-ligand interactions persist in the solution phase. The high concentration, low-temperature emission spectrum (5:5:1 ethanol:methanol:DMF) reveals a 740-nm band indicative of -M oligomerization, a 650-nm band attributable to tpy -interactions, and a 470-nm band characteristic of mononuclear [Pt(tpy)Cl]+ -* emission. Concentration-dependent absorption spectra were fit to a "two-dimer" model, yielding equilibrium constants for the formation of Pt-Pt-, and tpy-tpy-bound dimers of 1.3(1) x 10* 123 and 1.0(1) x 103 M-1, respectively, in 0.1 M aqueous NaCl. The low temperature solid-state luminescence of [Pt(tpy)Cl]+ is assigned to a 3(MMLCT) (MMLCT = metal-metal-to-ligand charge transfer) transition. The energy of this band is highly dependent on the counterion (PFe-, CIO4-, Cl-, CF3SO3-), in line with the different colors of these various salts. In contrast, the room-temperature solid-state emission spectra are more difficult to interpret. While the red perchlorate salt exhibits a relatively narrow emission band at 725 nm (red-shifted from the 77-K maximum at 695 nm), consistent with a 3(MMLCT) transition, the orange (Cl-, CIO4-, CF3SO3-) and yellow (PFe-) salts have extremely broad room-temperature emission bands that all appear at nearly the same energy (Amax ~640 nm). We assign this luminescence to an eximeric intraligand transition resulting frominteractions and propose that the temperature dependent emissions from the orange and yellow solid materials originate from multiple electronic states.

A new class of coordinatively unsaturated, monomeric organoscandium compounds, Cp*2Sc-R (Cp* = (rj5-C5Me5); R = halide, hydride, alkyl, alkenyl, alkynyl, aryl), has been prepared. Cp*2Sc-Cl is obtained from reaction of ScCl3(THF)3 (THF = tetrahydrofuran) with LiCp*, and Cp*2Sc-R (R = CH3, C6H5, C6H4CH3, CH2C6H5) from treatment of Cp*2Sc-Cl with the appropriate organoalkali reagent. These organoscandium compounds react with dihydrogen rapidly to yield R-H and Cp*2Sc-H. The tetrahydrofuran adducts Cp*2ScX(THF) (X = Cl, H, CH3) are obtained upon treatment of Cp*2Sc-X with tetrahydrofuran. Rapid exchange of dihydrogen with the hydride ligands of Cp*2Sc-H and Cp*2ScH(THF) occurs even at low temperatures. Other alkyl derivatives may be conveniently prepared by treatment of Cp*2Sc-H (or Cp*2ScH(THF)) with -olefins, e.g., Cp*2ScCH2CH3 from Cp*2Sc-H and ethylene. Aliene and Cp*2Sc-H afford Cp*2Sc(7j3-C3H5). Cp*2Sc-R (R = H, CH3, aryl) reacts with pyridine to yield Cp*2Sc(C, N-j;2-C5H4N), which crystallizes in the orthorhombic space group

A series of organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared. Variation of the counterion (anion) in many cases leads to materials with large powder second harmonic generation efficiencies, the highest of which is roughly 1000 times that of a urea reference.

I I;/ 'Mir~1llud11 %.1111111Ld1 OULY m1ulg11ln %'.lr11111 L1y V JU ragr, :7 1J O.UUU1LK31PIUMUIilLdi radgr I Table S1. Crystal and Intensity Collection Data for Pt(bpm)Cl 2 .0.5(nmp) (3) Formula: C 8 C1 2 H 6 N 4 Pt.0.5(C 5 H 9 NO) Formula weight: 473.72 Crystal color: Red Habit: Short needle Crystal Size: 0.10 x 0.19 x 0.31 mm pale = 2.38 g cm-3 Crystal System: Monoclinic Space group: C2/m (no. 12) a = 12.668(4) A b = 15.618(6) A) = 93.43(3)0 c = 6.704(3) A V = 1324.0(8) A 3 Z = 4 Lattice parameters: 25 reflections, 100 < 0 < 150 p. = 112.1 cm-1 Absorption correction: none Enraf-Nonius Cad-4 diffractometer w scans MoKa, A = 0.7107 A Graphite monochromator 20 range: 2-50'-15 < h < 15-18 K k < 18,0 < 1 < 7 T = 294 K Number of reflections measured: 2539 Number of independent reflections: 978 Number with F' > 0: 900 Number with F' > 3c(F2): 793 Standard reflections: 2 every 150 min. Variation: within counting statistics GOFmerge: 1.30 for 978 multiples Rmerge: 0.035 for 778 duplicates Number used in refinement: 978 Criterion: All reflections used Final R on F: 0.031 for 793 reflections with F > 3a(F2)

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