d⁸⋯d¹⁰ Rh^I⋯Au^I interactions in Rh 2,6-xylylisocyanide complexes with [Au(CN)₂]⁻: bond analysis and crystal effects

Abstract

The well-known [RhL4]n(anion)n structures, with RhI⋯RhI d8⋯d8 interactions, are replaced by others with RhI⋯AuI d8⋯d10 interactions such as [{RhL4}{Au(CN)2}] (L = 2,6-xylylisocyanide) or [{RhL4}{Au(CN)2}{RhL4}{Au2(CN)3}·4(CHCl3)]∞ when the anion is [Au(CN)2]−.

Mesogenic [Rh(L)4](A) complexes form mesophases with RhI⋯RhI-containing and triphenylene-discotic segregated columns. Effect of RhI⋯RhIinteractions and A−= [Au(CN)2]−on hole mobility

“…Small twists will be compatible with good p-p stacking and short RhÁ Á ÁRh distances in dimers. Large twists weaken the strength of the p-p stacking and bring to longer RhÁ Á ÁRh distances but are compatible with polymeric structures or, in the limit, to formation of monomers, as in the case of the yellow complex [Rh(CNXylyl) 4 ](BF 4 ), 10 whose X-ray diffraction structure consists of monomeric cation units, with no p-p stacking and no RhÁ Á ÁRh interactions.…”

“…The GIWAXS patterns of thin films of all the complexes display well-oriented columnar mesomorphic organizations, with [10] or [11] crystallographic directions aligned onto the film normal (Fig. S46, ESI †).…”

“…Independently of the configuration used for the measurements, the large 2D lattice parameters of the mesophases (a and b, Table S14, ESI †) and the distinct SAXS/WAXS signals, corresponding respectively to the metallic fragment and triphenylene parts, confirmed, in agreement with the detailed crystallographic analysis of reference compounds, that both multiblock [Rh(L D1 ) 4 ](A) and [Rh(L D2 ) 4 ](A) complexes selfassemble into multi-segregated columnar structures made of differentiated metal-containing piles and triphenylene columns, respectively. Also, whatever the experimental situation, the assembly of the metallic fragment part and counter-ion comes down to a platelet-like ''RhA'' subunit resembling to a ''discotic'' mesogen with even piling distance (3.53 Å for RhA in [Rh(CNXylyl) 4 ](BF 4 ), 10 close to the normal triphenylene stacking periodicity (h p E 3.5 Å for TPh), but obviously of different chemical nature. In the single-crystal structure of the compound [Rh(CNXylyl) 4 ](BF 4 ), analogue to [Rh(L D2 ) 4 ](BF 4 ) without alkoxytriphenylene substituents, the counter-ions locate in the same plane of the metallic centre and both superimpose (with lateral shift and inversion) to complex and counter-ions of the next molecular layer (Fig.…”

“…3 The appropriate combination of metal-metal interactions with other (donor-acceptor, hydrophobic-hydrophilic, cation-anion) attractive interactions facilitates the design of a vast range of functional nanomaterials such as sensors, nanowires, and ionic liquids. 1,3b-6 For a different reason, (Q)[Au(CN) 2 ] (Q + = cation) d 10 complexes also give rise to oligomeric complexes with AuÁ Á ÁAu interactions. In this case, where aryls are absent, it is the aurophilic interactions that help to overcome the electrostatic repulsion between the [Au(CN) 2 ] À anions.…”

“…9 Surprisingly, the synthetic possibility of combining [Au(CN) 2 ] À and [Rh(CNAr) 4 ] + complexes in molecular systems, which might facilitate the formation of compounds with RhÁ Á ÁAu interactions by cation-anion electrostatic attraction, had apparently been disregarded. Our group recently published a mixed [Rh(CNXylyl) 4 ][Au(CN) 2 ] system, in which the contribution of the anion-cation attractive forces between d 8 [Rh(CNXylyl) 4 ] + and d 10 [Au(CN) 2 ] À gives rise, in the solid state, to different crystals (sometimes different polymorphs) displaying d 8 Á Á Ád 10 short distances. The casual choice of the commercial CNXylyl (L X , Chart 1) as ligand was fortunate because the presence of two ortho Me groups in this isocyanide induces some reluctance to the formation of the multiple intra-unit p-p stackings observed in other [Rh(CNAr) 4 ] + cationic complexes and leads instead to the formation of polymetallic arrangements where RhÁ Á ÁAu interactions are preferred (Fig.…”