Polymorphic Crystal Approach to Changing the Emission of [AuCl(PPh₃)₂], Analyzed by Direct Observation of the Photoexcited Structures by X-ray Photocrystallography

Abstract

The photoexcited charge-transferred state of [AuCl(PPh(3))(2)] in a novel polymorphic crystal form was directly observed by X-ray photocrystallographic analysis. Its photoexcited state was completely different from the one generated in the known crystal of [AuCl(PPh(3))(2)]; the photoexcited bond-shrunk state was generated in the known crystal. This difference in the generated photoexcited state was clearly reflected by the difference in emission color. While the known crystal form showed green phosphorescence, the novel form showed blue phosphorescence under UV irradiation. The difference in the generated photoexcited state was due to the differences in steric hindrance in the crystal; bond shortening by photoexcitation was sterically allowed in the known form, while on the other hand, it was restricted in the novel form. Therefore, instead of the bond-shrunk state, the charge-transferred excited state became the lowest triplet state, and the emission color changed from green to blue (i.e., a blue shift of the emission wavelength was observed). These results mean that the photoexcited structure and the emission color of [AuCl(PPh(3))(2)] can be controlled by designing the molecular environment in the crystal.

Di‐ and Trinuclear Gold Complexes of Diphenylphosphinoethyl‐Functionalised Imidazolium Salts and their N‐Heterocyclic Carbenes: Synthesis and Photophysical Properties

“…Although the AuÀP bond lengths are in the usual range (P1ÀAu1 2.324(2) and P2ÀAu1 2.330(2) ), compared with [(Ph 3 P) 2 Au] [BF 4 ], [73] the AuÀCl distance of 2.709(2) is remarkably long and thus points to a weak bond. The bond length is considerably longer than for typical AuCl complexes (see compound 1 for example), as well as for trigonal planar compounds such as [AuCl(PPh 3 ) 2 ] (d(AuÀCl) = 2.5257 ) [74] and lies in the range between their atoms' covalent (2.38 ) [75] and Van der Waals radii (3.4 ). [76] This may be a result of five hydrogen bonds (d(HÀCl) = 2.5-2.8 ) found for each chlorine atom, which keep the anions inside the cavities of the macrocycle.…”

Coinage Metal Complexes of the Carbenic Tautomer of a Conjugated Mesomeric Betaine Akin to Nitron

“…However, to the best of our knowledge only two structurally characterized example are known to date with 1,2,4-triazol-5-ylidene ligands in this context [ 67 ]. In view of the comparatively weak, more phosphine-like donicity of 1,2,4-triazol-5-ylidene ligands a three-coordinate structure cannot be ruled out with certainty, therefore, similar to structures determined for a variety of phosphine complexes of the type [AuCl(PR 3 ) 2 ] [ 68 , 69 , 70 , 71 ].…”

A second polymorph of chlorido(hydroxydiphenylphosphane)gold(I)

“…Due to the nearness of the respective data collection temperatures, we disregard an interpretation of this result as indicating that the structure had undergone a significant phase transition between 173 and 195 K, and thus conclude that the structure of complex (I) presented here is a genuine polymorph and not the consequence of a phase transition. Indeed, polymorphs of chlorogold(I) phosphine complexes are relatively common (Healy, 2003) and often display interesting photochemical properties (Hoshino et al, 2010).…”

“…Polymorphs of chlorogold(I) phosphine complexes are relatively common (Healy, 2003) and often display interesting photochemical properties (Hoshino et al, 2010). For the previously reported polymorph of the title compound, see: Hollatz et al (1999).…”