[2+2] Photodimerization in the Solid State Aided by Molecular Templates of Rectangular Macrocycles Bearing Oxamidato Ligands

Abstract

A series of binuclear half-sandwich iridium and rhodium complexes bearing oxamidato ligands [Cp*2M 2 (μ-N,N′-bis(aryl)oxamidato)Cl 2 ] (1a, M = Ir, aryl = Ph; 1b, M = Ir, aryl = C6H4-p-Me; 2a, M = Rh, aryl = Ph; 2b, M = Rh, aryl = C6H4-p-Me) functioned as potential ‘‘organometallic clip’’ linear templates were synthesized by the reactions of the lithium salts of oxamide with [Cp*MCl2]2 (M = Ir or Rh), respectively. Treatment of the binuclear complexes (1a−2b) with trans-1,2-bis(4-pyridyl)ethylene (4,4′-bpe) in the presence of AgOTf (OTf = CF3SO3) gave the corresponding tetranuclear complexes of general formula [Cp*4M4(μ-N,N′-bis(aryl)oxamidato)2(μ-4,4′-bpe)2](OTf)4 (3a, M = Ir, aryl = Ph; 3b, M = Ir, aryl = C6H4-p-Me; 4a, M = Rh, aryl = Ph; 4b, M = Rh, aryl = C6H4-p-Me) in high yields. Confirmed by the single-crystal X-ray analysis, the molecular structures of tetranuclear complexes 3a and 4a showed that two binuclear fragments as building blocks were connected by μ-4,4′-bpe to construct a rectangular cavity with the dimensions 5.58 × 13.59 Å (3a) and 5.55 × 13.65 Å (4a). The two μ-4,4′-bpe ligands in 3a and 4a are close to each other within 4.2 Å to allow the [2+2] photoreaction in the solid state, which was proved by 1H NMR of the resulting products (5a−6b′) and single-crystal X-ray analysis.

Construction of Tetranuclear Macrocycles through CH Activation and Structural Transformation Induced by [2+2] Photocycloaddition Reaction

“…The central metal atoms are coordinated by one N atom of the bpe ligand and one O atom and one C atom from fumarate, forming a tetranuclear macrocyclic architecture. The lengths of the Ir(1)ÀN(1), Ir (1) (17), and 1.538 (17) , similar to those reported in previous works. [17] As shown in Figure 8, the interpenetration in 4 causes p···p interaction (3.433 ) between Cp* groups from a metallamacrocycle and another interaction along two directions (i.e., a and b axes).…”

“…The lengths of the Ir(1)ÀN(1), Ir (1) (17), and 1.538 (17) , similar to those reported in previous works. [17] As shown in Figure 8, the interpenetration in 4 causes p···p interaction (3.433 ) between Cp* groups from a metallamacrocycle and another interaction along two directions (i.e., a and b axes). Chains of the interval metallamacrocycles are parallel to each other, and the distance between them is 4.1 (from one macrocycle to another).…”

Self-Assembly of Cationic, Hetero- or Homonuclear Ruthenium(II) Macrocyclic Rectangles and Their Photophysical, Electrochemical, and Biological Studies

“…Although simple in design, these structures have shown promising applications as anion sensors and hosts for small molecules. 8 These rectangles typically incorporate a single type of metal ion. However, a second metal can be introduced into the donor component of the self-assembly, potentially imparting unique or enhanced functionalities in the form of mixed-metal, heterometallic scaffolds.…”

One-step synthesis of oxamidato bridged fac-Ru(CO)3 core based dinuclear compounds: Spectroscopic and structural characterisation

“…The second step of reaction was further supported by similar reactions of analogous chloro bridged p-cymene complex of ruthenium with a variety of bridging ligands to form dinuclear areneruthenium based half-sandwich p-cymene complexes [48,49].…”

“…Wang and co-workers have prepared oxamide based near infra red active electrochromic ruthenium compounds under basic conditions [39,40]. Therrien [48,49]. Although a variety of ruthenium based dinuclear complexes with different bridging ligands are available as aforementioned, reports on the synthesis of oxamidato bridged ruthenium analogues are scarcely available out of which fac-Ru(CO) 3 core based compounds remain unexplored.…”