Infrared (IR) probes based on terminally blocked β-cyanamidoalanine (AlaNHCN) 1 and p-cyanamidophenylalanine (PheNHCN) 2 were synthesized, and the vibrational properties of their CN stretch modes were studied using Fourier transform infrared (FTIR) and femtosecond IR pump-probe spectroscopies in combination with quantum chemical calculations. From FTIR studies, it is found that the transition dipole strengths of the cyanamide (NHCN) group in 1 and 2 are much larger than those of the nitrile (CN) group but comparable to those of the isonitrile (NC) and azido (N) groups in their previously studied analogs. The CN stretch frequencies in 1 and 2 are red-shifted from those in their nitrile analogs but more blue-shifted from the NC and N stretch frequencies in their isonitrile and azido analogs. The much larger transition dipole strength and the red-shifted frequency of the cyanamide relative to nitrile group originates from the n → π* interaction between the N atom's nonbonding (n) and CN group's antibonding (π*) orbitals of the NHCN group. Unlike aliphatic cyanamide 1, aromatic cyanamide 2 shows a complicated line shape of the CN stretch spectra. Such a complicated line shape arises from the Fermi resonance between the CN stretch mode of the NHCN group and one of the overtones of the phenyl ring vibrations and can be substantially simplified by deuteration of the NHCN into NDCN group. From IR pump-probe experiments, the vibrational lifetimes of the CN stretch mode in 1 were determined to be 0.58 ± 0.04 ps in DO and 0.89 ± 0.09 ps in HO and those in 2 were determined to be 1.64 ± 0.13 ps in CHOD/dimethyl sulfoxide and 0.30 ± 0.05 and 2.62 ± 0.26 ps in CHOH. The short time component (0.30 ± 0.05 ps) observed for 2 in CHOH is attributed to the vibrational relaxation through Fermi resonance. These vibrational lifetimes are close to those of the nitrile and azido groups but shorter than those of the isonitrile group. Consequently, cyanamide behaves like an apparent vibrational hybrid of nitrile and isonitrile in that cyanamide is similar to nitrile in vibrational frequency and lifetime but to isonitrile in transition dipole strength. It is believed that cyanamide has the potential to be a strongly absorbing IR reporter of the conformational and environmental structure and dynamics of biomolecules in comparison to nitrile, a weak absorber.

Alkyne IR probes 1–6 with Si and S (or Se) atoms incorporated into the CC bond were synthesized, and the vibrational properties of their CC stretch mode were studied using FTIR and femtosecond IR PP spectroscopies and quantum chemical calculations.

Local probes are indispensable to study protein structure and dynamics with site-specificity. The isonitrile functional group is a highly sensitive and H-bonding interaction-specific probe. Isonitriles exhibit large spectral shifts and transition dipole moment changes upon H-bonding while being weakly affected by solvent polarity. These unique properties allow a clear separation of distinct subpopulations of interacting species and an elucidation of their ultrafast dynamics with two-dimensional infrared (2D-IR) spectroscopy. Here, we apply 2D-IR to quantify the picosecond chemical exchange dynamics of solute−solvent complexes forming between isonitrile-derivatized alanine and fluorinated ethanol, where the degree of fluorination controls their H-bond-donating ability. We show that the molecules undergo faster exchange in the presence of more acidic H-bond donors, indicating that the exchange process is primarily dependent on the nature of solvent−solvent interactions. We foresee isonitrile as a highly promising probe for studying of H-bonds dynamics in the active site of enzymes.

Two new heterometallic metal–organic frameworks (MOFs), LnZnTPO 1 and 2, and two homometallic MOFs, LnTPO 3 and 4 (Ln=Eu for 1 and 3, and Tb for 2 and 4; H3TPO=tris(4‐carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of the C3‐symmetric ligand H3TPO with the corresponding metal ion(s) (a mixture of Ln3+ and Zn2+ for 1 and 2, and Ln3+ alone for 3 and 4). Single‐crystal XRD (SXRD) analysis revealed that 1 and 3 are isostructural to 2 and 4, respectively. TGA showed that the framework is thermally stable up to about 400 °C for 1 and 2, and about 450 °C for 3 and 4. PXRD analysis showed their pore‐structure distortions without noticeable framework–structure changes during drying processes. The shapes of gas sorption isotherms for 1 and 3 are almost identical to those for 2 and 4, respectively. Solvothermal immersion of 1 and 2 in Tb3+ and Eu3+ solutions resulted in the framework metal‐ion exchange affording 4 and 3, respectively, as confirmed by photoluminescence (PL), PXRD, IR, inductively coupled plasma atomic emission spectroscopy (ICP‐AES), and energy‐dispersive X‐ray (EDX) analyses.