Template Synthesis of Macrocyclic Complexes: A Laboratory Project for Advanced Undergraduate Students

Abstract

A family of tetraazamacrocyclic complexes of nickel(II) forms the basis of a convenient synthetic experiment for advanced undergraduates, highlighting the utility of the coordination template effect in promoting macrocyclic synthesis.

Nickel(II) Cyclidenes with Appended Ethylpyridine Receptor Centers as Molecular Tweezers for Dicarboxylic Acids

“…A systematic blue shift in the series I , II , and III is seen for the charge-transfer bands. Very similar trends in UV−vis spectra have been reported previously for Jäger and cyclidene complexes with variable ring size. , The absorption bands in UV−vis spectrum of III (λ max (ε) 336 (37 030), 368 (25 710), 435 sh nm (570), see Experimental Section) are almost identical to the spectrum of the analogous benzyl-substituted cyclidene prepared by Cameron and co-workers (λ max (ε) 333 (39 800), 363 (19 950), and 443 nm (10 00)), thus confirming a similar electronic structure of these two compounds and indicating the lack of pyridine coordination in III .

3 UV−vis spectrum of I − III in acetonitrile at room temperature: I (solid), II (dashed), III (dotted).

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“…The UV−vis spectra of compounds I − III in acetonitrile reveal the usual features for square-planar nickel(II) cyclidene complexes: , the broad absorption bands with λ max at 430−480 nm due to d−d transitions and the charge-transfer bands between 330 and 410 nm (Figure .) As the macrocycle ring size increases from 14- to 16-membered, the d−d transition is blue shifted.…”

“…As the macrocycle ring size increases from 14- to 16-membered, the d−d transition is blue shifted. This can be explained by the fact that increasing the tetraaza macrocycle size increases the metal− nitrogen distances, which, in turn, increases the HOMO−LUMO gap . The d−d transition in II, however, is very similar in energy to that in I , possibly due to distortion of the 15-membered macrocycle.…”

“…Chemicals (reagent grade or better) and anhydrous solvents were purchased from Aldrich or Acros and used as received. Starting dimethoxy cyclidenes [Ni[(MeOEthi) 2 Me 2 [14]tetraeneN 4 ]](PF 6 ) 2 , [Ni[(MeOEthi) 2 Me 2 [15]tetraeneN 4 ]](PF 6 ) 2 , and [Ni[(MeOEthi) 2 Me 2 [16]tetraeneN 4 ]](PF 6 ) 2 were prepared according to published procedures. − All measurements were recorded at 298 K, unless otherwise noted. The 1 H and 13 C NMR spectra were recorded on a Bruker DPX-300 spectrometer and referenced to residual solvent resonance peaks.…”

“…[16]tetraeneN 4 ]](PF 6 ) 2 were prepared according to published procedures. [73][74][75][76] All measurements were recorded at 298 K, unless otherwise noted. The 1 H and 13 C NMR spectra were recorded on a Bruker DPX-300 spectrometer and referenced to residual solvent resonance peaks.…”