Photodynamic therapy (PDT) has received considerable attention in recent years as it could present a valuable alternative to conventional cancer treatment. Promising in vitro and in vivo tests have already been carried out and the first photosensitisers have been approved for clinical applications. Nevertheless, it is evident that the photosensitisers currently in use are not optimal and that more suitable sensitisers are required. The development of new sensitisers with improved properties for photodynamic therapy is therefore indispensable and a great deal of research is being carried out in this area. This thesis is concerned with the synthesis and the evaluation of novel, acetylenic NIR-chromophores which are expected to have a potential as photosensitisers in photodynamic therapy applications. The synthetic strategy employed is to utilise vicinally dialkynylated 1,2-diones as versatile building blocks for the rapid assembly of the targeted acetylenic dyes. It is demonstrated that octaalkynylated tetrapyrazinoporphyrazines, phthalocyanines, and tetra-[6,7]-quinoxalinoporphyrazines are synthetically accessible in few steps using this methodology. All of the novel dyes exhibit strong absorptions with high extinction coefficients in the red or NIR region and significantly bathochromically shifted absorption maxima compared to those of their non-acetylenic counterparts, rendering them interesting as sensitisers in the photodynamic treatment of cancer. Ideally, a suitable sensitiser for photodynamic therapy should be soluble in bodily fluids, i.e. in aqueous media. Since the initially prepared new chromophores are highly lipophilic, the second part of this work deals with the synthesis and the photophysical assessment of more hydrophilic derivatives of these dyes. It is also established qualitatively that the new chromophores possess the ability to generate singlet oxygen upon irradiation with light, which is an essential prerequisite for a useful PDT agent.