We present the electrodynamic response of TiOBr, which undergoes a transitionto a spin-singlet ground state for temperatures below T$_{C1}=28$ K. Thetemperature evolution of the phonon anomalies indicates, like in \cl, anextended fluctuation regime, extending well above T$_{C1}$. At low frequencies,the spectral weight is progressively suppressed by decreasing the temperature,suggesting the formation of a spin-gap and a considerable electron-phononcoupling. A comparison of the two oxyhalides shows a weaker interplane couplingand reduced dimensionality for TiOBr that enhances fluctuations and shifts theordering temperatures to lower values. In the fluctuation regime thetemperature dependencies of some phonon parameters track the temperatureevolution of the magnetic susceptibility.
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