Homohelicity induction of propylene-linked zinc bilinone dimers by complexation with chiral amine and α-amino esters. Preorganization of structurally coupled homohelical subunits

Homohelicity induction of a series of propylene-linked zinc bilinone (ZnBL; linear tetrapyrrople-zinc(II) complex) dimers upon complexation with chiral amine and α-amino esters was investigated. Introduction of substituents such as dimethyl and diisobutyl to the central carbon of the propylene spacer gave rise to stabilization of the homohelical (PP and MM) conformers rather than the heterohelical (PM) conformer. As bulkiness of the substituent increased, stability of the homohelical conformers was raised. The preorganization of the homohelical structures led to significantly amplified homohelicity induction upon complexation with chiral amine and α-amino esters.     

Efficient syntheses of new chiral peptidomimetic macrocycles through a configurationally driven preorganization

A new family of 32-membered ring peptidomimetic macrocycles has been efficiently obtained in a simple one-pot two-step reductive amination reaction, from easily prepared precursors. The structural and stereochemical variables have been explored in order to rationalize the obtained selectivity. The formation of the [2A+2B] tetraimine intermediate has been explained in terms of a very favorable configurationally driven preorganization as detected by NMR, CD and molecular modeling.     

Macrocyclic versus acyclic preorganization in organoplatinum(Ⅱ)-based host-guest complexes

Two host-guest systems have been constructed,by employing structurally similar terpyridine platinum(Ⅱ) macrocycle and molecular tweezer as the synthetic receptors.The macrocycle/guest complex displays low-energy emission signal,reinforced non-covalent binding affinity,and enhanced photosensitization capability than those of the molecular tweezer/guest one.The discrepancy between macrocyclic and acyclic preorganization modes originates from the different numbers of Pt(Ⅱ)…Pt(Ⅱ) metal-metal bonds in host-guest complexation structures.     

Macrocyclic versus acyclic preorganization in organoplatinum(II)-based host-guest complexes

Two host-guest systems have been constructed,by employing structurally similar terpyridine platinum (II) macrocycle and molecular tweezer as the synthetic receptors.The macrocycle/guest complex displays low-energy emission signal,reinforced non-covalent binding affinity,and enhanced photosensitization capability than those of the molecular tweezer/guest one.The discrepancy between macrocyclic and acyclic preorganization modes originates from the different numbers of Pt (II)...Pt (II) metal-metal bonds in host-guest complexation structures.     

Benzene-based tripodal isothiouronium compounds as sulfate ion receptors

Novel benzene-based tripodal isothiouronium receptors are synthesized for the selective recognition of tetrahedral oxoanions. The binding study by isothermal titration calorimetry indicates that the cationic receptors bind sulfate ions preferably in a tripodal mode, while they show a mixed binding mode toward phosphate ion. The tripodal isothiouronium receptors show large ΔG⁰ values toward sulfate ions in methanol, which are entropy driven. The results demonstrate that a subtle structural constraint can lead to different binding modes toward structurally similar anions.     

Synthesis of nano-scale shape-persistent macrocycles via hydrogen bonding-promoted formation of amide and hydrazone bonds

This paper describes the synthesis of two series of rigid macrocycles from hydrogen bonding-induced folded aryl amide and hydrazone oligomers that bear two amines or one amine and one aldehyde. The diamines reacted with diacyl chloride to produce amide macrocycles, whereas the latter underwent self-coupling reactions to afford imine macrocycles. DFT calculations revealed that the new macrocycles possess rigid planar conformations and their cavity diameters were estimated to be 1.86 nm–2.75 nm.     

Synchronous helicity control in zinc bilinone trimer

In order to develop an artificial signal transmission/amplification system triggered by chiral recognition, we synthesized a series of zinc bilinone (ZnBL) trimers bearing a tripodal spacer and investigated homohelicity induction by complexation with chiral α-amino esters. Controlling the length of the peripheral alkyl groups in ZnBL moieties led to preorganization of the trimer to homohelical conformers. In addition, complexation with chiral α-amino esters induced the formation of the chiral homohelical conformer in which three ZnBL moieties adopted the same helicity.     

Preorganization—From Solvents to Spherands

This article assesses the importance of molecular preorganization to the rapidly developing field of complexation involving designed synthetic organic compounds. Since its birth as a science, organic chemistry has drawn heavily on biological chemistry as a vast storehouse of evolutionary structures, reactions, and control mechanisms that serve as inspiration for designed organic-compounds mimics. Biological systems, through highly structured complexation, accomplish complicated tasks. The receptor sites of enzymes, the genes, the antibodies, and ionophores possess high degree of preorganization. In other words, their functional groups act cooperatively as binding or catalytic sites which are largely collected and oriented prior to complexation.—The strength of the organic chemist derives from his ability to design organic compounds, organic reactions, synthetic sequences, and test systems to evaluate hypotheses. The design of highly structured complexs and the discovery of the rules that govern their behavior are described here. Research in this field is particularly rewarding because scientific and aesthetic content merge and become visible in the structures of many of the complexes.     

Assembling a Heterobimetallic Actinide Metal-Organic Framework by a Reaction-Induced Preorganization Strategy

Periodically arranging coordination-distinct actinides into one crystalline architecture is intriguing but of great synthetic challenge. We report a rare example of a heterobimetallic actinide metal–organic framework (An-MOF) by a unique reaction-induced preorganization strategy. A thorium MOF (SCU-16) with the largest unit cell among all Th-MOFs was prepared as the precursor, then the uranyl was precisely embedded into the MOF precursor under oxidation condition. Single crystal of the resulting thorium-uranium MOF (SCU-16-U) shows that a uranyl-specific site was in situ induced by the formate-to-carbonate oxidation reaction. The heterobimetallic SCU-16-U exhibits multifunction catalysis properties derived from two distinct actinides. The strategy proposed here offers a new avenue to create mixed-actinide functional material with unique architecture and versatile functionality.