Multi‐Component Coordination‐Driven Self‐Assembly: Construction of Alkyl‐Based Structures and Molecular Modelling

Abstract

The design of supramolecular coordination complexes (SCCs) is typically predicated on the use of rigid molecular building blocks through which the structural outcome is determined based on the number and orientation of labile coordination sites on metal acceptors, and the angularity of the ligand donors that are to bridge these nodes. Three-component systems extend the complexity of self-assembly by utilizing two different Lewis base donors in concert with a metal that favors a heteroligated coordination environment. The thermodynamic preference for heteroligation provides a new design principle to the formation of SCCs, wherein multicomponent architectures need not employ only rigid donors. Herein, we exploit the self-selection processes of bis(phosphine) Pt(II) metal centers which favor mixed Pt(pyridyl)(carboxylate) coordination spheres over their homoligated counterparts, specifically using alkyl-based dicarboxylate ligands instead of traditionally rigid phenyl, alkenyl, or ethynyl variants. Using this mode of assembly, flexible-based 2D and 3D SCCs containing long alkyl chains were synthesized and characterized. Density functional theory (DFT) and natural population analysis (NPA) calculations were performed on model systems to probe the thermodynamic preference for heteroligated coordination spheres in the experimental systems.

Synthesis and photophysical studies of self-assembled multicomponent supramolecular coordination prisms bearing porphyrin faces

“…In contrast, multicomponent approaches also permit the use of structurally ambiguous ligands, provided the remaining building blocks enforce a proper degree of directionality. As such, alkyl-based building blocks may be used in such selfassembly schemes, despite the fact that rotation about the carboncarbon bonds means that a single orientation of the coordination vectors is not maintained (57).…”

Pt(II)-Coordinated Tricomponent Supramolecular Assemblies of Tetrapyridyl Porphyrin and Dicarboxylate Ligands: Are They 2D Bow Ties or 3D Prisms?

“…C( 33)-C( 32)-C( 31) 121( 3) C( 33)-C( 32)-H (32) 119.3 C( 31)-C( 32)-H (32) 119.3 C(32)-C( 33)-C (28) 122( 3) C( 32)-C( 33)-H (33) 119.1 C( 28)-C( 33)-H( 33 Symmetry transformations used to generate equivalent atoms:…”

“…C( 31) 4895( 14) 6427( 11) 3566( 19) 105( 8) C (32) 4492( 15) 6219( 12) 3203( 19) 118( 9)…”

“…Expanding the scope of coordination-driven self-assembly strategies, researchers have recently discovered that cis-capped Pt(II) and Pd(II) corners can simultaneously bind a carboxylate and a pyridyl ligands, preferentially yielding thermodynamically favored heteroleptic Pt(N,O) complexes instead of two different homoleptic complexes. [29][30][31][32][33][34][47][48][49][50][51][52][53] Furthermore, when two different homoleptic Pt II (COO -)2 and Pt II (pyridyl)2 complexes were mixed together at an appropriate stoichiometry, they spontaneously reorganized into thermodynamically more stable heteroleptic Pt(N,O) complexes. 30,32,33 These revelations paved the door for metal-driven self-assembly of tricomponent metallacycles and cages containing two complementary ligands that further diversified their structures, properties, and functions.…”

“…While it is fairly straightforward to assemble 2:2:4 tricomponent rectangles 30,32,41 containing two parallel dicarboxylate and two parallel dipyridyl arms held together by four heteroligated Pt II (N,O) corners and 2:3:6 trigonal prisms 30,32 featuring two cofacial trigonal ligands and three ditopic linkers connected by six heteroligated Pt II (N,O) corners, to promote the formation of 2:4:8 tricomponent tetragonal prisms featuring two cofacial tetratopic (tetrapyridyl or tetracarboxylate) ligands and four ditopic (dicarboxylate or dipyridyl) linkers, one must judiciously choose these ligands to ensure that the ditopic linkers can only connect the tips of two cofacial tetratopic ligands via eight heteroleptic Pt(II) corners. 30,32,35,36 This is extremely important because if a ditopic linker is able to bridge two adjacent binding sites of the tetratopic linker via shared Pt(N,O) corners, then they are likely to form 1:2:4 bow tie (⋈) complexes instead of 2:4:8 tetragonal prisms via thermodynamically favored heteroleptic coordination since the former would be entropically more favored over the latter.…”