Steric Control of a Bridging Ligand for High-Nuclearity Metallamacrocycle Formation:  A Highly Puckered 60-Membered Icosanuclear Metalladiazamacrocycle

Abstract

A novel S4-symmetric icosanuclear manganese metalladiazamacrocycle was synthesized using a pentadentate ligand, N-3-phenyl-trans-2-propenoylsalicylhydrazide (H3L), that has a rigid and bulky terminal N-acyl group. A 20 cyclic repeat of an--(Mn-N-N)--linkage resulted in a highly puckered diaza-bridged 60-membered icosanuclear metallamacrocycle. The steric interaction between the ligands in the cyclic system leads to five consecutive Mn(III) centers in a chemically different--(Mn(A)Mn(B)Mn(C)Mn(D)Mn(E))--environment, with the chiralities of the metal centers being in a rather complicated--(LambdaLambdaDeltaLambdaLambda)(DeltaDeltaLambdaDeltaDelta)--sequence.

Novel 18-membered hexanuclear metallamacrocycle: Synthesis, crystal structure, and magnetic properties

“…2. in the temperature range 2-300 K. The molar effective magnetic moment l eff = (8 v m T) 1/2 of 1 decreased slightly with the temperature from 5.12 l B at 300 K to 2.83 l B at 40 K. Blow 40 K, it rapidly decreased to 0.42 l B at 2 K. This behavior suggests a weakly coupled antiferromagnetism, which is confirmed by a fitting to the Curie-Weiss expression v(T) = C/[T + H] with C = 16.9 cm À3 K mol À1 and H = À13.5 K using the data within T > 40 K. This behavior is similar to those reported for the other metallacrowns [24,25]. Compound 1 is made by six Mn(III) entities with the ligand amshz 3À linked between them, giving a cyclic system.…”

Synthesis, biological evaluation, and structure–activity relationship study of novel cytotoxic aza-caffeic acid derivatives

“…17 In order to obtain significant insight into the impact of activity on molecular diversity, compound 91, possessing two connected nitrogens in a seven bond linker length, was synthesized via a two step reaction starting from salicylic acid methyl ester (89, Scheme 3). 18 The structures of these compounds were confirmed both by mass spectrometry and 1 H NMR spectral data.…”

“…The aza-caffeic acid derivatives (31-44, 59-63) with an eight bond linker (B) were coupled by potassium salts of substituted cinnamic acids (12)(13)(14)(56)(57)(58) and N-substituted 2-chloro acetamides (23)(24)(25)(26)(27)(28)(29)(30) under the activation of potassium iodine with yields of 56-87% (Scheme 1). 14 Compounds 9-11, which were further hydrolyzed by potassium were synthesized by coupling the corresponding amines (15)(16)(17)(18)(19)(20)(21)(22) to chloroacetyl chloride. 15 The preparation of 53-55 was achieved as previously described by the appropriate substitution of benzylbromides and syringaldehyde (52).…”

A mixed-type of azametallacrown containing [Mn6(pnhz)6(DMF)4(H2O)2] and [Mn6(pnhz)6(DMF)2(H2O)4] constructed by a flexible pentadentate ligand

“…Among the MCs, diaza-bridged metallacrowns (azaMCs) have gained ever increasing concern in the field of supramolecular chemistry, self-assembly and host-guest chemistry for their fascinatingly symmetrical multi-nuclear frameworks [5][6][7][8][9][10][11] and their potential applications as secondary building units (SBUs) in the construction of 2-or 3-D metal-organic frameworks (MOFs) through the bridging exo-bidentate ligands [12,13]. The self-assembly of the high-nuclear azaMCs with rigid N-terminal ligands has been intensively and, to some extent, successfully investigated [14][15][16][17][18][19][20][21][22][23][24], while of less interest is the exploration of the highly flexible N-terminal groups in such system, which may adjust various geometric modes to satisfy the requirements of assembly process and lead to interestingly structural topologies. Moreover, only few examples have been reported concerning the flexible N-terminal ligands, where diversely geometric configurations of the ligands are involved in one kind of 18-MC-6 [25,26].…”