Importance of π-Interactions Involving Chelate Rings in Addition to the Tetrel Bonds in Crystal Engineering: A Combined Experimental and Theoretical Study on a Series of Hemi- and Holodirected Nickel(II)/Lead(II) Complexes

Abstract

Five heteronuclear nickel(II)/lead(II) complexes with two compartmental reduced Schiff base ligands were prepared and characterized. Their structures were confirmed by single crystal X-ray diffraction analyses. In each complex, nickel(II) is placed in the inner N 2 O 2 compartment and lead(II) in the outer O 2 O 2 ′ compartment of reduced Schiff base ligands. Interesting molecular architectures were formed via supramolecular interactions in the solid state of the complexes. A density functional theory study is devoted to analyze unconventional tetrel bonding interactions established between the σ-hole at the hemicoordinated lead(II) and either the electron-rich thiocyanate or the π-system of the aromatic ligand. In addition, π-stacking assemblies between both the aromatic rings and fivemembered Pb-chelate rings were described and studied both with regard to their energies and by using the noncovalent plot index.

Polyoxovanadates with Ethylidene-Pyridine Functionalized Bisphosphonate Ligands: Synthesis, Structure, Spectroscopic Characterization, Magnetic, and Antibacterial Studies

“…The π–π stacking (side-wise π–π overlap between two aromatic rings of two different polyanionic units) distance of separation between the two pyridine rings is 4.3474 and 3.4459 Å, for polyanions 1 and 2 , respectively. This range of 3.5–4.5 Å is ideal for such interactions to exist. , The arrangements of the rings are also influenced by dipolar interactions between the C–N bonds, with the bonds being arranged exactly anti to each other in both 1a and 2a [see Figure S6­(a) and S7­(a), respectively, in Supporting Information].…”

“…This range of 3.5 -4.5 Å is ideal for such interactions to exist. [65][66] The arrangements of the rings are also S6 in Supporting Information]. Thus, the presence of significant voids is observed in the solid-state arrangement of 3a, occupied with water of crystallization and counter-cations.…”

Enhancement of the Tetrel Bond by the Effects of Substituents, Cooperativity, and Electric Field: Transition from Noncovalent to Covalent Bond

“…[3] Added to the electrostatic attraction, polarization, and charge transfer play important roles, as does dispersion to varying degrees. [4] The TB has been the subject of growing study [5][6][7][8][9][10][11] due in part to its importance in numerous applications such as molecular recognition, [12][13][14] crystal materials, [15][16][17][18][19] chemical reactions, [20][21][22][23] and biological systems. [24][25][26][27][28][29][30][31][32] Frontera and coauthors, for instance, prepared several crystals utilizing a tetrel bond with other interactions in lead(II) complexes.…”

Tetrel Bonding and Other Non-Covalent Interactions Assisted Supramolecular Aggregation in a New Pb(II) Complex of an Isonicotinohydrazide

“…On the other hand, the coordination chemistry of Pb(II) gains particular interest from the large ionic radius of this heavy p-block metal ion, its rich variety of coordination numbers from 2 up to 10, and the peculiar feature of the 6s 2 lone-pair in the coordination sphere of its complexes [ 17 , 19 , 22 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. This lone-pair can be stereochemically active, which is called hemidirectional or non-active, for which the term “holodirectional” was coined ( Chart 1 ) [ 19 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. The background is the observation that the electron pair on the Pb(II) atom is either stereochemically irrelevant (holodirected) or demanding space (hemidirected) [ 17 , 19 ].…”

“…The hemidirected coordination allows Pb(II) to participate in the formation of tetrel bonds, which are of great importance for the resulting topology of Pb(II) coordination compounds [ 17 , 19 , 22 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Although the occurrence of hemidirected or holodirected bonding cannot be reliably predicted [ 19 , 28 , 29 , 30 , 31 , 40 , 41 ], recent work using polyfunctional multidentate ligands, such as carboxylates of 2-thiols or heterocycles [ 19 , 24 , 25 , 26 , 27 , 28 ], or the per se polyfunctional thiothiosemicarbazones, hydrazones, or Schiff base ligands of the salen or salan type [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ] allowed formation of tetrel bonds. We also have recentl...…”