Two new cryptands,
The commonly used paraquat guest
- NSF-PAR ID:
- 10047958
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Heteroatom Chemistry
- Volume:
- 28
- Issue:
- 6
- ISSN:
- 1042-7163
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 2 and4 , were prepared from bis(m ‐phenylene)‐32‐crown‐10 (BMP32) 5,5'‐diacid chloride and dibenzo‐30‐crown‐10 (DB30) 4,4'‐diacid chloride, respectively, by reaction with pyridine‐2,6‐dimethanol. The resultant cryptands2 and4 have the ester moieties reversed from the previously reported isomers,1 and3 . These “reverse” cryptands display lower association constants with viologen derivatives than the original cryptands; this is rationalized by the conjugation of the ester moieties with the aromatic rings, which reduces their electron‐donating properties and offsets the increased basicity of the pyridyl nitrogen atoms. The crystal structure of the BMP32‐based cryptand2 indeed confirms the coplanarity of the ester and aromatic moieties and indicates that, as a result, the available cavity is quite small and that the pyridyl nitrogen atom points away from the cavity. -
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Abstract Affinities of six anions (mesylate, acetate, trifluoroacetate,
p ‐toluenecarboxylate,p ‐toluenesulfonate, and perfluorooctanoate) for three related Pt2+‐linked porphyrin nanocages were measured to probe the influence of different noncovalent recognition motifs (e. g., hydrogen bonding, electrostatics, π bonding) on anion binding. Two new hosts of M6L312+(1b ) and M4L28+(2 ) composition (M=(en)Pt2+, L=(3‐py)4porphyrin) were prepared in a one‐pot synthesis and allowed comparison of hosts that differ in structure while maintaining similar N−H hydrogen‐bond donor ability. Comparisons of isostructural hosts that differ in hydrogen‐bonding ability were made between1b and a related M6L312+nanoprism (1a , M=(tmeda)Pt2+) that lacks N−H groups. Considerable variation in association constants (K 1=1.6×103 M−1to 1.3×108 M−1) and binding mode (exo vs.endo ) were found for different host–guest combinations. Strongest binding was seen betweenp ‐toluenecarboxylate and1b , but surprisingly, association of this guest with1a was only slightly weaker despite the absence of NH⋅⋅⋅O interactions. The high affinity betweenp ‐toluenecarboxylate and1a could be turned off by protonation, and this behavior was used to toggle between the binding of this guest and the environmental pollutant perfluorooctanoate, which otherwise has a lower affinity for the host. -
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Abstract The “masked” terminal Zn sulfide, [K(2.2.2‐cryptand)][MeLZn(S)] (
2 ) (MeL={(2,6‐iPr2C6H3)NC(Me)}2CH), was isolated via reaction of [MeLZnSCPh3] (1 ) with 2.3 equivalents of KC8in THF, in the presence of 2.2.2‐cryptand, at −78 °C. Complex2 reacts readily with PhCCH and N2O to form [K(2.2.2‐cryptand)][MeLZn(SH)(CCPh)] (4 ) and [K(2.2.2‐cryptand)][MeLZn(SNNO)] (5 ), respectively, displaying both Brønsted and Lewis basicity. In addition, the electronic structure of2 was examined computationally and compared with the previously reported Ni congener, [K(2.2.2‐cryptand)][tBuLNi(S)] (tBuL={(2,6‐iPr2C6H3)NC(tBu)}2CH). -
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Abstract The “masked” terminal Zn sulfide, [K(2.2.2‐cryptand)][MeLZn(S)] (
2 ) (MeL={(2,6‐iPr2C6H3)NC(Me)}2CH), was isolated via reaction of [MeLZnSCPh3] (1 ) with 2.3 equivalents of KC8in THF, in the presence of 2.2.2‐cryptand, at −78 °C. Complex2 reacts readily with PhCCH and N2O to form [K(2.2.2‐cryptand)][MeLZn(SH)(CCPh)] (4 ) and [K(2.2.2‐cryptand)][MeLZn(SNNO)] (5 ), respectively, displaying both Brønsted and Lewis basicity. In addition, the electronic structure of2 was examined computationally and compared with the previously reported Ni congener, [K(2.2.2‐cryptand)][tBuLNi(S)] (tBuL={(2,6‐iPr2C6H3)NC(tBu)}2CH). -
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1 , as well as [K(crypt)][Cp*2NdCl2],2 , and the previously reported [K(crypt)][Cp*2Nd(bipy)]. A mono‐Cp* Lu(III) complex, Cp*Lu(bipy)2,3 , was also found in an attempt to make Cp*2Lu(bipy) from LuCl3, 2 equiv. of KCp*, bipy, and K/KI. Surprisingly, the (bipy)1−ligands in neighboring molecules in the structure of3 are oriented in a parallel fashion with intermolecular C⋅⋅⋅C distances of 3.289(4) Å, which are shorter than the sum of van der Waals radii of two carbon atoms, 3.4 Å. Another product with one Cp* ligand per lanthanide was isolated from the reaction of [K(crypt)][Cp*2Eu(bipy)] with azobenzene, which afforded the dimeric Eu(II) complex, [K(crypt)]2[Cp*Eu(THF)(PhNNPh)]2,4 . Attempts to make4 from the reaction between Cp*2Eu(THF)2and a reduced azobenzene anion generated instead the mixed‐valent Eu(III)/Eu(II) complex, [K(crypt)][Cp*Eu(THF)(PhNNPh)]2,5 , which allows direct comparison with the bimetallic Eu(II) complex4 . Mono‐Cp* complexes of Yb(III) are obtained from reactions of the Yb(II) complex, [K(crypt)][Cp*2Yb(bipy)], with trimethylsilylazide, which afforded the tetra‐azido [K(crypt)]2[Cp*Yb(N3)4],6 , or the di‐azido complex [K(crypt)]2[Cp*Yb(N3)2(bipy)],7 a , depending on the reaction stoichiometry. A mono‐Cp* Yb(III) complex is also isolated from reaction of [K(crypt)][Cp*2Yb(bipy)] with elemental sulfur which forms the mixed polysulfido Yb(III) complex [K(crypt)]2[Cp*Yb(S4)(S5)],8 a . In contrast to these reactions that form mono‐Cp* products, reduction of Cp*2Yb(bipy) with 1 equiv. of KC8in the presence of 18‐crown‐6 resulted in the complete loss of Cp* ligands and the formation of [K(18‐c‐6)(THF)][Yb(bipy)4],9 . The (bipy)1−ligands of9 are arranged in a parallel orientation, as observed in the structure of3 , except in this case this interaction is intramolecular and involves pairs of ligands bound to the same Yb atom. Attempts to reduce further the Sm(II) (bipy)1−complex, Cp*2Sm(bipy) with 2 equiv. of KC8in the presence of excess 18‐crown‐6 led to the isolation of a Sm(III) salt of (bipy)2−with an inverse sandwich Cp* counter‐cation and a co‐crystallized K(18‐c‐6)Cp* unit, [K2(18‐c‐6)2Cp*]2[Cp*2Sm(bipy)]2 ⋅ [K(18‐c‐6)Cp*],10 .
