The research presented in this dissertation focuses on the synthesis, crystallization, and characterization of various gold(I) complexes. With every gold(I) crystal, intensive studies were conducted to uncover any luminescence, polymorphism, and/or response to environmental stimuli such as temperature, vapor, and pressure. All doctoral research performed in the Balch lab, including collaborations with other members as well as outside research groups, is not fully presented in this dissertation. A list of publications can be found at the end. Chapter 1 explores the role of anions and mixture of anions in crystals of bis(cyclohexylioscyanide) gold(I) cations, [(C6H11NC)2Au]+. A new crystal was synthesized and characterized with the (SbF6)− noncoordinating anion. The crystal displayed no known polymorphism unlike its previously synthesized (PF6)− and (AsF6)− analogues. However, by mixing combinations of anions and ratios of anions, an isostructural set of crystals were produced. Not only were thermochromic trends observed for mixed anion crystals with known thermochromic species but unexpected thermochromic properties appeared in mixed anion crystals that contained species with no thermochromism. In Chapter 2, the vapochromic and vapoluminescent properties of both [(C6H11NC)2Au](PF6) and [(C6H11NC)2Au](AsF6) were further investigated to uncover the first observed single-crystal-to-single-crystal phase transition, verified by single crystal X-ray diffraction, of both species. A rare case of a two-polymorph single crystal of each species was achieved as well. With no vapor molecules incorporated in these crystals, the mechanism of conversion was further examined at the macroscopic, microscopic, and atomic level to understand how these solvent-free crystals transform from solvent vapor exposure. Chapter 3 focuses on methods to isolate [(C6H11NC)2Au]+ to form non-luminescent crystals, which was achieved through bulky noncoordinating anions and solvent molecules. Newly synthesized [(C6H11NC)2Au](BArF24) was crystallized but showed no further interesting properties other than purposely isolating aurophilic interactions. However, the first solvates of these [(C6H11NC)2Au]+ series, C6H6·[(C6H11NC)2Au](AsF6) and C6H6·[(C6H11NC)2Au](SbF6), were crystallized that displayed a unique turning on of luminescence when left to dry that matched their solvent-free forms, as verified by powder X-ray diffraction, infrared spectroscopy, and fluorescence spectroscopy. Differing from the other studies, Chapter 4 examines the structure and luminescence of three-coordinate 2,2'-bipyridine gold(I) tertiary phosphine crystals. Separate isomorphic series of [(Ph3P)Au(bipy)]XF6 and [(Et3P)Au(bipy)]XF6 (where X = P, As, or Sb) along with binuclear [[mu]2-bipy(AuPPh3)2](PF6)2 were crystallized and showed no luminescence, which is unlike that of known strongly luminescent gold(I) phosphines. However, the three-coordinate [(Ph3P)Au(bipy)]XF6 and [(Et3P)Au(bipy)]XF6 complexes all displayed significantly unsymmetrical coordination of the gold(I) to the two nitrogen atoms in the 2,2'-bipyridine ligand. These large unsymmetrical distances were further investigated.