Sequence-Dependent Guest Release Triggered by Orthogonal Chemical Signals

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Trisiminopyridine ligands can self-assemble into Zn(II) coordination cages.
• These cages can exhibit selective guest binding and reactivity.
• Controlling molecular networks with chemical signals is a key challenge.

Purpose of the Study:

• To design a responsive molecular network using coordination cages.
• To investigate selective guest encapsulation and sequential release.
• To explore the potential of these cages for anion recognition.

Main Methods:

• Synthesis and characterization of three Zn(II)4L4 coordination cages.
• Guest encapsulation studies with chloroform and cyclohexane.
• Investigating the effect of tris(2-aminoethyl)amine (tren) and perrhenate on cage behavior.
• Spectroscopic analysis to determine binding constants and selectivity.

Main Results:

• Two cages selectively encapsulated chloroform and cyclohexane, respectively.
• Sequential release of guests was achieved using tren and perrhenate as chemical signals.
• A third cage, formed in situ, selectively bound perrhenate with high affinity (K(a) > 10(7) M(-1)).
• Tren's reactivity with the cage mixture controlled perrhenate uptake and release.

Conclusions:

• A molecular network responsive to distinct chemical signals was successfully designed.
• The coordination cages demonstrate tunable guest selectivity and controlled release capabilities.
• The high affinity for perrhenate suggests potential applications in nuclear medicine due to its similarity to pertechnetate.