Abstract
In this work we report the linear and non-linear IR spectral response characterization of the CO bonds of PenicillinG sodium salt in D2O and in DMSO−d6 solutions. In order to better characterize the spectral IR features in the CO stretching region, broadband middle infrared pump-probe spectra are recorded. The role of hydrogen bonds in determining the inhomogeneous broadening and in tuning anharmonicity of the different types of oscillators is exploited. Narrow band pump experiments, at the three central frequencies of β−lactam, amide and carboxylate CO stretching modes, identify the couplings between the different types of CO oscillators opening the possibility to gather structural dynamic information. Our results show that the strongest coupling is between the β−lactam and the carboxylate CO vibrational modes.
Highlights
Infrared spectroscopy and its evolution based on non-linear laser techniques achieved with ultrashort middle infrared (MIR) pulses are successfully used for the detection and the characterization of molecular systems with various degrees of complexity
Broader is the line width, in comparison to anharmonicity, larger is the compensating effect between the negative and the positive bands. From this qualitative considerations it is possible to conclude that the vibrational mode involving the β − lactam CO is less anharmonic than the other two vibrational modes and its anharmonicity increases from DMSO to D 2O solution
The CO stretching of carboxylate, β − lactam and Amide I vibrational modes in penicillin G sodium salt are characterized in terms of inhomogeneous broadening and anharmonicity by linear and non-linear MIR spectroscopic techniques
Summary
Infrared spectroscopy and its evolution based on non-linear laser techniques achieved with ultrashort middle infrared (MIR) pulses are successfully used for the detection and the characterization of molecular systems with various degrees of complexity. Their potential in routine analytical diagnosis is not yet well established and this is especially true for the non-linear techniques [1,2]. On molecules with medium/large size such as oligopeptides self-organization makes the systems more uniformly structured and it is easier to find spectroscopic studies [6,9,13,14,15,16,17]. This work represents an original study on a β − lactam system by means of linear and ultrafast non-linear MIR technique
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