Silver(I) complexes with oxazoline-containing tripodal ligands: structure variation via counter anions and reaction conditions

Seven new silver(I) complexes of the formula [Ag₂(L)₂(CF₃SO₃)₂] (1), [Ag₂(L)₂(CH₃SO₃)₂] (2) [Ag₂(L)₂](BF₄)₂ (3), [Ag₃(L)₂(NO₃)₂]NO₃·5H₂O (4), [Ag₂(L)(NO₃)₂]·CH₃OH (5), [Ag₂(L)₂](ClO₄)₂ (6) and [Ag₃(L)₂(CH₃CN)₃](ClO₄)₃ (7) have been synthesized by reactions of 1,3,5-tris(2-oxazolinyl)benzene (L) with varied silver(I) salts under different conditions. The influences of counter anions and reaction conditions on the structure of the complexes are discussed. Three complexes 1, 2 and 3 with two kinds of different 1D chain structures were obtained under the same synthetic conditions by using different silver(I) salts, and the ligand L was found to adopt bis-monodentate (1 and 2) and tris-monodentate (3) coordination modes respectively. On the other hand, by using the same silver(I) nitrate or silver(I) perchlorate but different reaction solvents, 4 and 5 or 6 and 7 were isolated respectively. Complexes 4 and 5 have different 1D chain structures, and 6 is isostructural with 3. However, 7 is a tri-nuclear, propeller-shaped M₃L₂ supramolecular capsule in which L adopts a cis,cis,cis-conformation, while the ligand L in 3–6 has cis,trans,trans-conformation. The results revealed that the nature of the counter anions, such as their size, coordination ability and coordination mode, and the reaction conditions all have great impact on the structure of the complexes. The complexes were also characterized by electrospray mass spectrometry. Furthermore, complex 7 exhibited modest second-harmonic-generation (SHG) efficiency.